Bottom line: By April 21, Google says you must have a mobile site or it will severely hinder your ability to reach customers. Why does Google care so much?
It's all about the user experience. Basically, Google is saying if you're not mobile you don't care about user experience and if that's the case — they don't care about you.
We’re not telling you that you need a responsive website aka mobile site because WE think they’re great, we’re telling you that you need a mobile site because GOOGLE is very demanding. Just like Prince's father. Read more.