Lifestyle inflation is definitely a thing, especially with a partner and kids. You're not going back to living in a crappy apartment with non-related roommates if you have a choice. And you don't want to give up nice trips and meals out.

Stepping off a well-paid career trajectory is also hard to do even if you're pretty sure you have enough savings to comfortably cover your annual living expenses. It can be hard to get back on if things don't go as planned. I've definitely known people who ended up pushing semi-retirement out a bit because work wasn't getting in the way of life too much and why not stash some more money away while the stashing is good?