Hmmm. I was under the impression that .50cals could do damage to armor, especially to the thinner top back armor, and that there was always a chance of tracking the vehicle. The .50s do work against halftracks and flak guns, although now that I think about it, perhaps that has more to do with the open top nature of those vehicles. Strafing vehicles is far too dangerous to be doing if there is no chance of damaging them.
Oh, while we're here, I often strafe GVs as a way to point them out to friendly GV'ers nearby. Is there a better way to accomplish that task? I don't have a very good GV-eye view of the world.
Strafing open-topped Wirbels & Ostwinds as well as Lvts, M3s and the like is fine - every gun in game can ot them out of action.
However strafing Tigers, and T34 with mere .50cals is almost worthless - but you still get the kill.
When I want to point those tanks out to my GV comrades on the ground, I just shoot the ground next to them. That's sufficient, and who cares if my attack hit % drops from 51.9 to 50.1 %

Of course, if I'm in Hurri D or Il-2 I shoot to kill

This is what I don't understand... how can I do so much damage that I get the kill credit while at the same time I do so little damage that I have to re-up three times to actually break parts by strafing?
It's how track damage is modeled. They basically "soak up" damage points. You may not have done enough damage to actually break them yet, but it may be still more damage points than that single 75mm round did that made the tank go "boom".