Everyone who actually wants the job (which is 99% of the ppl that interview) ask for feedback. Asking for feedback is & should be standard.
And when you ask for feedback, don't expect to hear the magic words on what will get you the job on the next interview. Most of the time, (unless your interviewing skills are legitimately poor to subpar) your feedback will sound a lot like a high school date rejection: "we like you a lot but we liked this other dude better."
And this really is because every unit is different (as what literally everyone knows already at this point) and some units will mesh with you better than others.
The main thing is (insert generic inspirational quote) don't give up and keep interviewing. It will stick sooner or later.