> as soon as sideloading is allowed, sideloading will become required by the most popular apps.

Android has always supported sideloading, yet in almost 10 years of using Android, I've never had to sideload any commercial app.

Anecdotally, Amazon has tried to push their app store for a while by incentivizing installs with free games and the like, but none of these weren't also available on the official Play Store. Nowadays, it's all free-to-play anyway, but that's a different topic.