No, the average Janes and Joes don't enable side-loading: it's a toggle, not enabled by default, it's in an advanced setting pane and it's good as it is. Google has been controlling what is installed through their Store and that is enough for 100% of average users. They have been doing it badly though, leaving many scams through, same for Apple. They should focus on this, not the advanced users.
>>Gigach+l
It's hard to find reasons to protect someone trying to install a shady app. Using that one reason to kill the possibility to install third-party apps for everyone is shady.