They can't attack it due to heavy Russian air defense, not due to lack of fighters.
For now, there is no functional difference between destroyed equipment and disabled equipment. Turning this disabled equipment into destroyed equipment carries risks for no immediate gains. (Granted, this might look like a poor decision in hindsight)
IANA… not L, but anyway. Maybe they're trying to attack a few bits and pieces so the convoy locks up lots of Russians and their equipment and can't be either resupplied or moved. (Tankers and other trucks would need to refueld the entire convoy.)