Martin Tournoij lays out a bunch of ways he finds zsh more compelling than bash.

There are many more things. I’m not going to list them all here. None of this is new; much (if not all?) of this has around for 20 years, if not longer. I don’t know why bash is the de-facto default, or why people spend time on complex solutions to work around bash problems when zsh solves them. I guess because Linux used a lot of GNU stuff and bash was came with it, and GNU stuff was (and is) using bash. Not a very good reason, certainly not one 30 years later.