"Why is blowing shofar forbidden on Shabbos? Because the worry is that a Lubavitcher chossid will want to go on mivtzoim to blow shofar for other Yidden and will bring the shofar with him."
— A joke
It's not like this is such a bad question. Chassidus also questions the fullness of logic for some of the justifications for rabbinic enactments, with the most famous example being not blowing shofar on Shabbos. Blowing shofar is an amazing mitzva, which literally renews the spiritual energy that sustains this enormous universe and the spiritual universes "above" it. And Chazal forbid doing it on Shabbos because there is a slight worry that some ignoramus may carry a shofar?
I think there are several ways to answer this.
First, which I call the Litvish way, is that such is the law. Hashem said in Torah to listen to Chazal, and whether it makes sense to you or not doesn't matter.
The second, which I call Chassidic way, is to say that the historical and social justifications are merely a kli, a vessel, for the mitzva.
Examining the validity of Chazal's reasoning (even if one were permitted to do so) is as useful as literally judging a book by its cover. Imagine you pick up a book that someone recommended to you as truly wonderful. For instance, The Master of Go. You look at the cover and say: "I really disapprove of the publisher's choice for the cover." OK. So what? Who cares about the cover? Even if does make no sense, why do you bother examining it when you have a chance to look inside?
We were sent into this world to make it into a dwelling place for Hashem. The mitzvos are instructions for doing so. We create the world into a dwelling place for G-d by purifying it spiritually and carrying out His Will in it. The fact that His Will expressed itself through rabbis being concerned about a low-probability event does not truly matter, just like it doesn't truly matter what cover a publisher chose for a book or what color is the binding.
(Make no mistake: the kelim for the mitzvos — the legal content of the laws, the description of the actual physical activities that one must, may, or may not do, as well as the physical activities themselves — are the only way we can have access to the oir that is the essence of the mitzvos. Furthermore, according to Chassidus, even if we had a direct access to the oir, it would still be preferable to access it through the physical world, since Hashem wants the dwelling specifically in the physical matter of the Universe, it being the lowest level where He can be revealed and therefore the ultimate way of expressing His Kingship.
My point is just that when we start worrying too much about the physical reasons for the mitzvos, we must remember that the binding of the book is there merely to hold the pages, and the pages and the ink are there only to transmit the ideas.)
So, the above two explanations are quite classic.
But I was thinking this morning that we don't necessarily understand the "cover" either. I am talking especially about the people like myself that are only starting out with learning Halacha. I remembered a conversation that I had with my rabbi about "politics" within Jewish communities.
I forwarded to him a letter, in which a friend of mine wrote:
I know that [a local OU representative and a rabbi] used to eat at [a local restaurant]. I've heard that he doesn't anymore, even though the standards were tightened across the Vaad several years ago. (Since he used to eat there when the standards may have been more maykil, it would seem to me that it's a 'political' issue for some, rather than a Halachic issue).
I do know that outside of Boston, the KVH is considered a widely accepted/respected Hashgachah (even internationally). It may be a local/polical issue.My rabbi objected to the statement "it may be a political rather than Halachic issue". He said: there is an idea of community standards. Members of a certain community may not trust a mashgiach or an organization that is lax on a certain aspect of Halacha, because the members of the community themselves chose to be makpid on these aspects. They are not necessarily saying that the food is treif, but they would rather "when in doubt, go without". (Furthermore, even if a person is not necessarily lax on kashrus, the fact that he is lax in another area of Halacha — according to the standards of this community — creates a worry about his overall level of observance.)
The same goes for the members of one community not trusting hashgacha from the members of another community. When the second community says themselves that their goal is to make Torah as accessible to the masses as possible, and therefore, they find a heter upon heter to justify the behaviors that members of the first community would not justify, the members of the first community choose not to trust the second community's members' hashgacha. It may be about "politics", but it is still a Halachic issue. It's not the sort of politics when the president of the shull doesn't like that the rabbi got the best parking spot and therefore tries to undermine him all the time. It's the sort of politics when you hear a cook say that he doesn't believe in the existence of bacteria and therefore washing hands after the bathroom is silly — and decide not to eat his food. Or if you don't go to a neurologist whom you heard proclaim that we only use 10% of our brain.
My point with bringing this example is to say that oftentimes we look at an issue, but without a proper application of logic or knowledge of all the facts. "Does it make sense that it is ossur to move a fork on Shabbos because back in the day, people used to stomp on grapes in their keilim on Shabbos?" The ultimate answers are the first two: whether or not it makes sense to you, it's the Will of G-d, and, furthermore, the historic reasoning for the mitzva is its superficial aspect anyway; the reason we don't move muktza is ultimately spiritual.
But I also think it's unwise to think that we know all the social circumstances under which the Chazal enacted a given takkanah and all the levels of the logic according to which it still applies today.
That's why I also think it is quite arrogant and unwise to say things like: "Keeping cholov Yisroel nowadays is completely ridiculous. There is no reason for it at all." Sure, this statement is wrong from the point of view of appreciation of the process of psak din (i.e., it doesn't matter what you think; it matters what our Halachic authorities think — and it matters what the specific authorities that are your authorities think, as well as what the general consensus is). But it may also be wrong in its appreciation of reality.