Why do exit surveys almost always give you the wrong reasons for churn?

People rarely type out a long paragraph explaining every little annoyance when they cancel a subscription they usually just check a generic box like "missing feature" or "too expensive" to get it over with. But when you actually look at session replays you notice users getting stuck on a weird button placement or a confusing login screen for three minutes straight before dropping off. Those tiny micro-frustrations add up yet nobody ever puts them in a feedback form.

What methods do you use to spot these hidden drop-off points?