Another reason for multiple accounts is to join rps you might not want to join on your "main".

Personally I have thought about making a alt of my own, but I've grown attached to this one. 

Many of my friends have an alt because you can join an rp without fear of someone else judging you based on past experience, or on the other hand, friends judging you on the rps you join.

There's nothing wrong with alt accounts, but having 2 is pretty tedious if you're using both. I slightly condone 3, but after that I doubt you're making accounts for a good reason, with the exception if you're ditching your old accounts of course. But if you're still gonna use your main, I would recommend just one alt.