The retention problem is definitely there. I have got one other person onto Hive but they didn't stay here for too long and they were mainly interested in Actifit or Splinterlands. Eventually they felt tired of it and moved on.
I prefer to curate by myself and I think building HP is a good thing. I have never powered down and I don't plan on doing so either.
Doing just 1-2 things on HIVE can be boring, especially Actifit and Splinterlands... When you get bored by the game, you quit... With Actifit is probably similar... If you don't find the community to share things/walks/experiences, you will get bored and quit... That's normal...
But, it's important to say that it really depends on what your friend was searching for here on HIVE. If he searched for community and friends, he would probably find some... If he searched for a quick buck on those two things, I suppose that's not what he got...