Well, it makes sense considering you can just destroy the cargo bay door with a couple of shots and get all the cargo.
It's much more difficult than that, mostly because it's very hard to hit the cargo hatch. It's hard to line yourself up on an evasive target to even see the cargo hatch, the roll rate makes it especially easy for your target to simply turn the other side of their ship to you. Secondly, most of the ships show the cargo hatch in the wrong position when targeted and the auto aim of weapons forces you to fire in that wrong position exacerbates this problem.
Also, mass disruption seems to have been turned off for some reason, meaning you cannot slow ships from entering supercruise the way you did before. Lastly, this is all moot if your target is trying to fight you.
Piracy in this state of the game has become much more a matter of shooting someone until they drop cargo or they die.