I see that users including myself at work do ssh to 127.0.0.1. In my case I do it as a different user and to a non-standard port as part of reaching my Linux work environment (the hosting). 

I wonder why I do that?

The command I use is `ssh username@127.0.0.1 -p xxxxx` where xxxxx is the port number (not port 22 but something completely different). 

The procedure is part of me inheriting old Linux installations at work. What would be the difference between `ssh user@127.0.0.1` and just `su user` ?