In table tennis, why is a ball that hits the edge considered in?

Question

The answer to this question states that a ball that hits any part of the top of the table (including the edge) is considered in-bounds.

My question is why is a ball that hits the edge (and bounces off the table in a manner that could be nearly impossible to return) considered in-bounds?

On all of the ping pong tables I've seen in people's homes, the white lines along the edges do not actually touch the edge of the table. There is about 2-3 millimeters of space between the white line and the edge of the table. This means that if a ball hits the edge of the table, it has landed beyond the white line and therefore should be considered out of bounds. If it is still considered in-bounds, then there is no point in having those white lines along the edges.

Do the tables used in ITTF matches have their white lines touching the edge? If so, then it makes sense for edge balls to be considered in-bounds. But if their tables have space between the edge and the white line, then it is illogical for edge balls to be considered in-bounds.

Answer 1

A complete amateur here...

I would say, it's far easier to tell the difference between the ball hitting the table or missing it, than between the ball touching a line than missing it. The balls just bounce and fly so quickly. And you judge basically by seeing whether the trajectory has changed (or by hearing). Spotting where the ball was at the moment of touching the table (on a line or not) is hard.

And with the lines - I suppose their purpose is not to specify the border of the valid play field. Rather they are for everyone to mark the size of the table clearly, in case the background doesn't give enough contrast with the table surface.