They know. But many people will look at the screw, see it's some weird thing they don't have a screwdriver for, and decide to take the car to an authorized dealership instead of trying to repair an issue themselves.

Some will just buy the special screwdriver. But that doesn't matter, what's important is that some won't, and the line goes up. You also have to look at it as yet another small barrier to repairability. It's not stopping you by itself, but every single barrier adds up and stops more people.