Answer

There are situations in which an enactment or law was established for some reason, and now the act itself is binding. Therefore we do not expound the reason for the verse, and we do not follow the reason for the enactment. In your opinion, can one accept the yoke of the Kingdom of Heaven without reciting the Shema, but in some other way? Or remember the tekhelet and the sky without having tzitzit on one’s garment? Can one bless the Holy One, blessed be He, in a different formula? Jewish law instructs regarding actions, not only regarding value-oriented goals. Even though, of course, various value-oriented goals underlie the practical obligations.
But estimates and presumptions are something else, because there it is clear that we are dealing with assessments of reality and not absolute determinations. Clearly, “a person does not repay a debt before its due date” is an assessment of reality and not a normative determination, and if reality changes one should not rule in favor of the lender. There are also such determinations in Jewish law (although the line is very thin. I will address this in the third book of the theology trilogy I am now writing), for example, things that are forbidden משום danger are forbidden because there is danger. And when there is no danger, there is no reason to observe them. The permission to kill a louse on the Sabbath is based on a factual perception, and once that was disproved, the permission is void. And so on.
Rabbi Soloveitchik’s remarks are well known, and personally I do not believe that he himself actually thought so. This is part of the struggle against Reform (in a distorted way, in my opinion). In any case, one way or the other, it is clear that this is nonsense. Presumptions were not given at Sinai; they were established by the Sages through observing their surroundings. And reality can change. There is such a tendency in a woman, but its intensity changes with the circumstances (and in principle I do not rule out the possibility that it could also disappear entirely from the world. That does not contradict anything), and the halakhic decisors have already noted this.
More generally, there is no such concept as authority over factual determinations at all. Authority exists only with respect to norms (and on this, in the second book of the above-mentioned trilogy).
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Orel:
I’m not sure I understand from this answer why we do not follow the reason for the enactment. The Sages instituted washing mayim acharonim because of Sodomite salt; why do we say that even though the reason has lapsed, the enactment has not lapsed?
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The Rabbi:
Simply put, this is a question of authority. We do not have a religious court that can repeal an enactment, and a matter established by formal count requires another formal count to permit it (and in rabbinic matters this requires a religious court greater in wisdom and number; see Maimonides, beginning of Chapter 2 of the Laws of Rebels, and the Kesef Mishneh there). Essentially this is a rule whose purpose is to strengthen and preserve the stability of Jewish law. But this means that in essence the enactment is indeed void when its reason is void.
However, it is brought in the name of the Vilna Gaon that enactments are not changed when their reason lapses for an essential reason, namely that they have hidden reasons. This is a very strange argument in my view, for several reasons: 1. In any interpretation one can claim that perhaps there is another explanation hidden from us. But we do not do that, because a doubt does not override a certainty. If we have a reasonable explanation, why assume that it is not correct and that there is another explanation? 2. Even if there is concern for hidden reasons, at most this creates a doubt. Either the reason we thought of is correct or it is not. But if it is correct, then the law is void, and therefore one should decide here according to the laws of doubt. Therefore it does not seem reasonable to me that this is an essential rule as the Vilna Gaon held; rather, we return to the questions of authority.
And after all that, I will only add that in many places the halakhic decisors do repeal enactments whose reason has lapsed, for a variety of reasons (and certainly in the case of Sodomite salt, which appears in the Shulchan Arukh itself at the end of the section, and this is an old matter). See my article here.