It is a verify active sailing centre with several races every week. We saw more boats going in and out than any other place we have docked. I got a crew spot on a few races just by asking around.
Good social life too
On the lack of power boats, there are few power boats in UK waters in general, relative to E Coast of the US.
Howth is a club. May be that power boats are not accepted. If they are, the power boaters would be short on people to talk to in the very large and very active bar at the club