Yes some sites are still using old versions however as releases are increased support goes away for older releases or become costly. A highlight of progression from 9.0 is 9.0 --> MCD 4.0 --> MCD 4.1 --> MCD 4.2 and soon to be MCD 5.0.
9.0 UR3 is approximately a year old and 9 ish releases behind the current. That is a rough give or take.