Side loading on Android is just a legal argument in courts, its made too complicated for normal users to use it.
The only apps I know which are exclusively distributed this way are stuff banned from the store or developer tools.
I didn't think branding them as developers would change anything.
Nobody which has a real choice seems to distribute this way despite lots of potential gains avoiding the Google tax.
Usually hacked apps to remove ads or give them premium features or all power ups for free.
Or sometimes malware that wouldn't pass store review.
OK, and the first time you do it, you get a warning and you have to enable loading apps from 3rd party sources.
That's not a viable distribution channel at scale and that's intended.