To be frank, the answer is that it does cause problems for users. I've read countless anecdotes at this point from both camps, some claiming that Arch never breaks and some saying that updates have broken their install.

I personally tried Arch in 2017 for a period of a few weeks, and updates broke my system twice (in different ways). I was able to fix both issues, but decided I didn't want to deal with that. I suspect the difference between the two camps is that those who claim that it doesn't break don't consider something they can fix a breakage.