:: broken record ::
Sure we have to give some suspension to belief on physics for a SciFi series, but @Vontoothskie is still right by the internal logic of the SW universe.
In general from every time we see it used, for a ship to be tractored, there's a small set of rules: The ship with the tractor had to be bigger than the target by at least some. The targeted ship had to be either unaware, disabled, or willing. There's some ability to resist it and break out but it's not easy. Occasionally a rule is bent but the other two still get followed when it does. Like quadrijets can affect something bigger, but they're tugs and would reasonably still have to affect something either willing or disabled as a tug should.
But ultimately, in combat situations tractors seem to be conspicuously absent in the available media. Vader's ship doesn't tractor the Tantive IV until it's disabled. DS1 doesn't use them to stop fighters at Yavin despite earlier hauling in the Falcon when caught unaware. Over Hoth the blockading ISDs don't get to lock on to the transports as they climb out. Vader's fleet eschews them at Endor when they could have been engaged to stop the Slash maneuver and keep Ackbars fleet at gun range. Amidalas ship slips by the separatist fleet under heavy fire but untractored in Ep1...
It's quicker to imagine that if we accept tractors work in combat, then pretty much no space battle in the universe makes sense. If we assume there's something that can foil them then we're good.
Edited by ForceSensitive/broken record