Any proof of that? Do note that Amazon App Store users are basically sideloaders, as well as fortnite players, etc. you sure about that 1% number?
Besides, however number of people sideloading is not the point. The point is, you can already do it on the majority platform. Harping on Apple to allow sideloading makes no sense, as if Android didn’t exist. Forcing Apple iOS to behave like Android is basically removing choice, as the two platforms is becoming more alike than different. Choice means having two different options, not two of the same options.