It can also depend on the structural/natural area where the defence is taking place.
Say somewhere like Toll station on Gibraltar. There are 3 main entry places where the PAC (or EU if that happens) try to attack. Because there is a lot of cover, it's obvious you use rockets to smash the enemy defenders off those small structures/catwalks.
In Toll station the defenders are usually focusing on their main entry point they're defending from attack (I.E. lose situational awareness). And it's always spread equally around these points to stop the attackers. If most of the attacking team can force a breach quickly on one of the entry areas, they can overrun the other defenders while they're still focusing on their own little defence area.
This is what I've seen, not on the
TG server but in nearly all situations I've seen on other servers, everyone is too focused on their main defend point, they lose awareness and die.