Absolutely. Your example, the App Store, and lots of other aspects of the iOS ecosystem are how Apple prevents most (not all) of the "tragedy of the commons" problems on that platform.
For instance, "no background services" and "you can't use up all the physical RAM" are both OS-level restrictions, not app-store-level restrictions.
The OS does what it can, but the OS is entirely out in the open to be hacked, bypassed, subverted, worked around and so on. A pair of human eyes and a private app scanning process does what the OS can't.
No, it's not perfect. It's not even great lately. But it'd be worse without it, as you can witness on desktop operating systems.