Exactly! Sleep mode is known to have issues. On off over the years multiple different operating systems have had issues with sleep modes. Hibernate just always works and it's quick.

Hibernate has to persist all used memory, and RAM just keeps getting larger too.

Hibernation with kernel lockdown on Linux doesn’t work yet. Background post from a few months back: https://mjg59.dreamwidth.org/55845.html

You have to copy things for hibernate and you don't for sleep. Also because you can go into/out of sleep quickly you can periodically wake back up for notifications. MacOS and some Linux distros do this.