Not allowing side loading make iPhones more secure. Which can be argued as a benefit for the consumer. Family members have been convinced to install suspect APKs on Android which has caused issues.

Any reasonable consumer that would want to sideload apps, would know that isn't available for iPhones. As there are alternatives with Android I don't see forcing Apple to allow side loading to be in the interest of the consumer. They can purchase a range of equivalent phones that do allow side loading.

If apple was the only major smartphone maker, or made smartphones that outclassed all other devices significantly. Then they should be forced to allow side loading. But that's not the case right now. Consumers can sideload on other devices. Consumers that want sideloading won't purchase iPhones.

Forcing apple to sideload only benefits businesses and scammers/hostile actors. People can easily be guided to change settings to sideload, without understanding the consequences of it - warnings don't do much.