Also, memory limits -- it's very easy to overflow the max memory of some robots when the program includes many unnecessary lines.
And robots tend to run better with a smaller number of points, spaced further apart -- below a certain point spacing, even simple LIN motions can start having problems because the distance between points becomes too small for approximation to be calculated fully within the reach of the advance pointer.
And, related to MOM's post above, CIRC motions can have issues with points too close together.
I'm not sure how Spline motions behave with excess points.
But the bottom line is, if a point isn't necessary, it should be deleted. Even CNC CAM software does this, because some CNC machines start "stuttering" when too many points are programmed at too small a spacing.