Considering you’re on lemmy, I think it’s safe to assume you’re good with technology. Imagine someone in your life who isn’t good with technology trying to install the Epic Games store (without assistance)

First they have to track down the toggle to allow “unknown sources” (it’s never in the same place on all Android phones, they move it so that it’s hard to find), which presents a scary and vague warning about malware that a non-techie will never understand. Then they have to track down and install the APK, which presents even more scary warnings, then they get pestered by a “Play Protect” dialog which gives google permission to remotely disable the app (and the dialog can’t be permanently dismissed, so everyone will agree eventually)

Think about how you could run a successful app store in that environment. The cost of user acquisition is very high compared to Google. The only way to do it is to strike deals with OEMs to ship with your store, but Google has been caught either threatening or bribing these manufacturers to not accept those deals from competitors. Additionally, Google pays full time engineers to analyze competitors stores to search for vulnerabilities, and then leak them to the press before they get a chance to patch them, just to scare people away.

There’s probably more stuff I’m forgetting. This is all stuff that came out years ago when Epic first launched their store and got into public fights with Apple and Google. There are articles from back then that really go into the details if you’re interested in the topic.