There is a difference between hard and soft DRM. Soft DRM can be only some watermark, not keeping you from creating copies for your own devices. Hard DRM aims to prevent any copying.
In my experience soft DRM is very common, hard DRM not so much.
It hasn't changed, and I don't know why people are saying that most books don't have DRM. It is only a small minority.
Tor books is the largest publisher without it (owned by Macmillan). Otherwise everything is truly hard DRM either ACSM with epub or Kindle's. They are both more or less easily defeated though.
In my experience soft DRM is very common, hard DRM not so much.