Learning how to use vim...I want to know why people choose to use it

Highly recommend this talk : https://robots.thoughtbot.com/maste...
(watch it, its my reason to use vim too ;)

After a little customisation it is a very good editor. It is the best when programming on a laptop with a crap mouse as you don't need it. In my experience even if you don't use it every day it is very useful when you need it.