People like Frenchy, funked, etc in their 51Ds (Bs too in 190A5, but they are too rare), P47s, Spit9s and Typhoons, for the same reasons Karnak said, and because they like saying things like what Funked said; it's a good provocation.
GVs but Osties in particular are a pleasure to disable by guns from above, it is quite a rush to go through one or five GVs' tracer streams and come out with a kill, repeatedly, almost as much adrenaline as..
Going after high divebombers, CV divers the most common, and hitting them before they hit anything.
A good large thick spread of canon hit sprites on B17s, it would be MA heaven to do nothing but rake B17s to and fro while they shoot that uber 50 cal (radiator) poison at you.
Wingtip damage on Lancasters,
Putting as many rounds as possible in Ki67s without blowing them up,
MGing a fast M8's tracks or any GV bobsledding down a steep slope.
Shooting down a well flown spit9 is a pleasure, they are almost impossible to beat twice with the same move, but nothing comes close to P51 or P47 duels, it is really cool to shoot down a plane which is a better dogfighter strictly speaking in flying terms (eventually it will take over in a fight without weapons), is also able to out ping you from further, is as fast as you, and is probably convinced your plane is so much lesser than his.
I fly D9 almost all the time and it's easy to agree the mustang is better; but it is just too ugly and generic compared to my D9 to make one give up wanting to fight it.
And then an la7 comes by and shoots one of the two down as the denouement was about to happen.