I'm not sure that group values the lack of side-loading specifically. I think what they do value is the additional security and privacy benefits provided by a platform that strictly controls the distribution of its apps.
To the extent that the lack of side-loading helps prevent the spread of malware and shady apps stealing user data, I think they value it indirectly.
Android has serious malware problems. Even Epic's attempt to distribute Fortnite off the Play Store has directly led to fake APKs being distributed to unsuspecting users.
I don't see how you can open up iOS to side-loading without exposing it to the exact same malware problems Android has.
To the extent that the lack of side-loading helps prevent the spread of malware and shady apps stealing user data, I think they value it indirectly.
Android has serious malware problems. Even Epic's attempt to distribute Fortnite off the Play Store has directly led to fake APKs being distributed to unsuspecting users.
I don't see how you can open up iOS to side-loading without exposing it to the exact same malware problems Android has.