I find that it's very effective at providing a "collective memory". People come and go, but as long as they document what they did in a ticket that information

I find that it's very effective at providing a "collective memory". People come and go, but as long as they document what they did in a ticket that information is easy to search and can save a lot of effort. And by "document" I don't even mean a fancy design doc and pages of spec. Just a few sentences on why something was done, or a couple of copy-pasted command lines used for testing or reproducing a bug can be a big help.