The thing with B-Wings is that they are so reliable it makes everyone want to use them. The system slot makes them even more reliable at whatever it is you're looking for them to do.
You don't need to be lucky in rolling defense dice, it just tanks the hits. It puts out a good amount of firepower and is very maneuverable.
In a tournament setting, Dagger & Blue Squadron pilots are very much worth the points. You know what you're going to get out of them and taking them isn't risky.
Since most people play in tournament formats (even in pickup games) they see a lot of use.