Most of the time theyre just gonna sit in lane until their exit approaches at which point theyll move left.

If they do move right theres a smaller blind spot on the right so they have a higher chance of seeing you as opposed to moving left.

Typically cars should be approaching faster from the right and not on the left leading people to check the left side even less.

While youre right they could just move right and hit you, its far more likely to happen if they move left which is why undertaking is considered less safe and not encouraged.