your disc players, tv's, and sometimes also your media players on your computer all can do the same thing
Exactly--and a TV or computer monitor does this very accurately, because it knows the target resolution of the display screen. There's no need to upscale a lower-resolution video and make a new file from it, which is going to be considerably larger that the original.
The exception would be if someone is using some AI software that actually sharpens things up using a complex algorithm that analyses each frame and then produces a clearer result. Some uploaders here have tried to do this (with mixed results), and this can be an improvement. But simply stretching each frame and quadrupling file size offers no benefit.