Adding features adds complexity. Features interact with each other in complex ways. If you add a feature and don't know quickly if it broke another feature, that costs time.

Letting the users find the bugs costs time - you have to talk to the user, replicate the bug report, find the failure, fix it, and then release. Finding that same bug 2 minutes after you wrote it (and before it got released) is massively quicker.

This feels like one of those "write code 16 hours a day to make more progress!" things that experience has taught me just doesn't work in practice. I feel like I'm making a lot of progress, but after about 10 hours most of the code I write is pure shite and needs to be rewritten the next day. I've found that it's actually way faster to quit coding after 8-10 hours rather than spend 2 hours the next day rewriting everything I wrote in the last 6 hours the day before.