I have no idea why, I'm fluent with touchscreens in the usual way but something in my brain just.... I don't know. Theoretically it should be the same, right? Except it feels horrible and wrong and I even have trouble trying to find the button.
Probably because I'm vision-impaired and an actual touchscreen is usually backlit and easier to see, while for physical buttons I've always compensated by using my sense of touch more (move hand towards general area of button, narrow it down with my fingertips).
The lack of the tactile click also certainly has something to do with it as pointed out above.
I'd actually be really interested to know from any UX design people here that work on this kind of thing - am I an outlier or does everyone hate them?