Idle thought - In Cisco IOS, why does the command 'wr' do a write memory?

Every other command that isn't specific enough will ask you what you are talking about, but 'wr' goes ahead and saves your config. Maybe I wanted a 'wr t' or something. The command does say 'mem' is the default, but it's kind of an important command to be loosy goosy with. I've wondered about it for years.