The problem is that most normal people (HN is not normal - mostly for the better) don't even understand what sideloading is - let alone actually care.
How can we fix this?
(aside from making people care - apathy enables so many political problems in the current age, but it's such a huge problem that this definitely isn't going to be the impetus to fix it)
Calling it "sideloading" instead of "installing" software successfully cements the notion that it is somehow not a completely normal thing to do. That's problem solved for the Googles and Apples of the world.
See the history of "jaywalking".