It is not a popular class of software to the masses, it is a popular class of software to a niche audience. I don't share as pessimistic attitude as OP though. I'm pretty sure the audience is in the tens of thousands!
Hard experience taught us that churn is just crazy high, no matter how compatible it easy to use you make it. Getting tens of thousands of stars is not the hard part because it's such an easy concept to like. But I would be surprised there are more than let's say ten thousand piholes in active use.