The simplest reason is that installing fail2ban is just as easy. Also, I sometimes want to know about failed attempts, mostly for legitimate attempts that fail

The simplest reason is that installing fail2ban is just as easy. Also, I sometimes want to know about failed attempts, mostly for legitimate attempts that failed and shouldn't have. As in: "why couldn't bob connect the the server?", and failed attempts would just show that he used the wrong password, or at least, that it is a password related problem.