Originally and primarily, to prevent people from just camping resupply points and constantly lobbing ordinance in rapid succession at targets from relative safety. It got carried over to ground, then naval and helicopters.
It's more or less meant to solve the infinite ammo problem that arises when you give unlimited resupplies.
You ran out of rocket stock. Have to buy more once you get back to hangar.
this ^
...and why is this mechanic in the game?
To make you frustrated and spend money?
Originally and primarily, to prevent people from just camping resupply points and constantly lobbing ordinance in rapid succession at targets from relative safety. It got carried over to ground, then naval and helicopters.
It's more or less meant to solve the infinite ammo problem that arises when you give unlimited resupplies.