Compare that to distributing apps on the internet where you have to trust each software provider with your credit card credentials and even if you do trust the vendor, there is a certain amount of friction just entering your payment information all over the internet.
I much prefer handling all of my subscriptions through iTunes even for services that use other places like Hulu, Netflix, and PluralSight.
Did you ever try to distribute a mobile J2ME app on mobile before the Apple and Google app stores? I know indie PC developers love Steam.
I'm very hestitant to download random software on Windows because of crapware/malware. I'll download iOS apps with abandon from the shadiest developers because I know they can't really do that much harm.