IMO PvP is very popular,
There are two metrics for this, one is as a percentage of the overall playerbase, and one is having critical mass (exceeding a certain minimum number).
In a CG system you are more likely to find other players, and some of those will be hostile. The fun comes in when there are enough players AND enough goodies & baddies to either hide in the crowd or attack with impunity.
There are times when there are too many baddies for the available pool of goodies, and that's frustrating for both sides (overfishing). So switch sides every so often