It's not about lock-ons in particular, it's just the sheer amount of different things you need to keep in mind. If you're flying, you get constantly locked-on, but if you're in a ground vehicle you get critically damaged from people suicide rushing C4s onto your tank, throwing them off buildings or just parachuting in on top of your tank.
It's like how there's this mine meta right now and the streets are full of dozens of mines at each intersection. Yes, you can shoot them, but there are just way too many and it isn't fun. I'd much rather have people make the conscious decision about which class they should play to deal with a certain situation.
If support can heal, resupply and destroy vehicles just turns them into a super soldier where they can do everything. It leads to the spam of C4 and it makes all other classes less relevant.