> GPS absolutely needs to adjust for the variable rotational speed of the earth
Sure, but that's a spacial thing, not something that's relevant to timekeeping. (There's technically a change in relativistic time dilation, but it's less than a rounding error - about five millimeters per second at the equator makes 1.000000000002388402 versus 1.000000000002388457 if I've got my math right. (The relativistic time dilation from the earth's rotation is itself a rounding error.))
And when you’re using GPS to find your location on the surface of the earth… spatial things matter, right? GPS is for figuring out your location, not what time it is.
You can use it to figure out what time it is, but that’s a side effect not the goal.
Sure, but that's a spacial thing, not something that's relevant to timekeeping. (There's technically a change in relativistic time dilation, but it's less than a rounding error - about five millimeters per second at the equator makes 1.000000000002388402 versus 1.000000000002388457 if I've got my math right. (The relativistic time dilation from the earth's rotation is itself a rounding error.))