From what I've read on this forum and on reddit, a lot of people seem to believe that keratinization and subsequent desensitization of the glans is a result of the friction between the delicate skin and underwear. I have a different view on that.
A lot of men here are waiting for keratinization to occur just by exposing their glans to air and underwear, but I think that there is absolutely no way of inducing keratine adaption just by the slight friction against the fabric past a certain point. Assuming you have comfortable underwear without any sharp seams, there shouldn't be enough friction to damage the skin and cause keratine build up.
The reason some circumcised men have such a rough and patchy skin on their glans is because they don't have enough skin to masturbate by gliding the skin and therefore rub it which is even with lube very damaging to the skin. Those who have enough skin to masturbate normally should have almost exactly the same sensitivity as uncircumcised men do because they don't cause any damage to their glans. That's the reason why some circumcised men report losing a lot of sensitivity while others don't. There is also a death grip syndrome where circumcised men have to rub their tip harder and harder to feel anything, commiting to the vicious cycle. I mean, it's logical, look up some pics on r/softies for example. Men with looser cuts seem to have completely normal looking glans whole those with higher cuts have much rougher and discolored skin there (although not always because there is a range of masturbation styles).
I read some posts on r/circumcisiongrief where users wrote about the fact that their tip used to be very sensitive just up until puberty when they started masturbating and only then got significantly less sensitive, supporting my theory. Also, a lot of men there have had a hard time adjusting to looser boxers when switching from briefs in the early teens and I heard a lot about those evil nets in swimmimg shorts.
I think that if you just expose the glans to underwear and air, the skin will dry out a little bit which may make it seem like it's less sensitive, but the head is naturally sensitive only to touching while moist (try it out, it is definitely the case), and you're not actually getting any keratinization done unless you were very sensitive in the first place. The only real adaptation that happens is that the brain learns to ignore the microsensations caused by the movement in underwear, but when you get it to be moist again, there shouldn't really be any difference.
What do you think? I think it makes sense and it's logical. From my own experience, I'm almost a week in and the head is still as sensitive as before, I just don't feel the movement as much as I used to. The glans is definitely drier and looks a bit beat up and hopeless from all the new and constant sensations; sometimes when I cross my legs and accidently squeeze it or something, there are some pressure marks, but overall nothing really damaging, so it only makes sense that the sensitivity is retained.