Every time the technical sophistication required to install apps from anywhere but Google's store (I don't love the term "sideloading" since it kind of denormalizes the act) is increased, the chances anyone will put in the effort to distribute apps any other way goes down. It also means apps Google doesn't want in its store are less likely to get made; I'd really like to see something that prioritizes notifications for me, for example, and I think that's against Google's rules.

I'm sure making it harder to obtain software outside a first-party app store provides some protection to some users from scams, but I really don't want that to be the answer. I don't claim to have a good one myself.