While it is fun to practice this type of formation flying, outside of refueling, there is no real "need" for this.
Sure there is.
Do you need tandem takeoffs and formation landing?
Do you need wingtip formation en-route?
Depends on the weather.
Not really, and if you ever need to go heads down while in close formation... well, try it to see how "scary" it can be.
If you're on the wing in fingertip, you don't go heads down. Period. If you need to, you fly out to route and do it there. That's proper procedure. No, you don't need permission.
Do you need this formation during combat? Hell no. If you are in close formation and AAA comes up, it'll probably get the wingman if it's aimed at the lead. Plus the wingman is pretty much useless as "cover" in a shooter-cover attack if he's this close anyway.
It isn't a combat formation. Shooter-cover is a tactic that has little to do with formations other than what formation you're supposed to get into after you complete your attack. Formations are part of tactics, not the other way around.
Funny how people seemed to jump on my "useless" comment... I'm just saying there is no practical use of this aside from "looking cool."
They jumped on it because you are wrong. This sort of formation is useful in weather penetration, certain navigation maneuvers, overhead landings, and it helps you hone precision flying and good flight safety skills. The only reason to think this sort of thing isn't useful is because the purpose of the formation, as well as the benefits of practicing it are not understood.
Same deal with contact flying - most vPilots just don't do it.
You don't even have to do this type of formation when refuelling, unless you're the one taking fuel.
Or if you want to exercise proper refueling procedure and do quick-flows.