First of all its not as bad as may have been said here, yes it will blur a bit when running on a lower resolution than on the original screen, yes it will be significant. It will however still be perfectly playable, just try it yourself by turning down the resolution in game or in windows, it will still be acceptable. It will look worse than otherwise possible but in truth its not nearly unplayable at lower resolutions. So while I would say a DPI scaling setting would most definitely be preferred if included it is certainly not a must have, running the game at a lower resolution would also be perfectly fine.
One other thing to keep in mind, some players still play on 27 or some 30 inch screens with the same resolution as a 21/23 inch screen 1920x1200 or 1920x1080 those people could also benefit from dpi scaling, instead of the UI being blown up way to much they could get it back to more reasonable sizes.
One other thing people need to keep in mind dpi of a laptop should generally be higher than the dpi on a laptop than again the dpi on a television. As distance increases items should also scale up.
The last factor is also personal preference, some people like elements smaller than others it just is that way.
All those things point in favor of a setting over a system that detects it.