It is nice when you can use an existing bike for a while to find out what works and what sucks.
What made me switch from an occasional commuter to daily were dyno lights, fenders, and a handlebar bag.

Dyno lights make it a hop-on and go affair, always ready, no worries about going ninja part way home.
Fenders simply keep maintenance down and my shorts dry.
Handlebar bag keeps the stuff I need handy without forgetting, and holds just enough clothes and stuff for the usual routine.
Also nice to have larger tires, which don't need air every day, and float over less than perfect pavement.

So my rando bike made the perfect commuter. N minus 1.