The scary check box exists for a reason. The reason malware isn't everywhere on android and iOS is because randomly installing apps isn't unsafe. I mean sans play store's automatic tools occasionally letting nonsense through.

A large part of the security model on both systems is the ability to constrain what apps can do, and by ensuring those have happened.

The various privileged (in the security sense) sandbox entitlements on iOS can't be used by a malicious app because the malicious app can't get through the App Store. That significantly increases the bar for any malware. I assume the Google Play store similarly limits access to privileged system features, and I would fully expect the 3rd party stores do not.

Also personally: The Epic store is a terrible app, and signing up for it requires providing vastly more information to them than I ever wanted to, especially for only a single company's games, from a company that has no stated intent of reducing data collection and improving privacy. A company that also engages in scummy tactics like loot boxes, virtual currency, etc