Not arguing, just discussing, I thought.
The passcode lock does have the option of kicking back in within a minute though, which is pretty short. Or, you can just get in the habit of every time you put the phone down, pless the on/off/sleep button to activate the lock (assuming you have it set to lock immediately).
Limiting access to wifi or cellular data though adds a layer of inconvenience I think most people would complain about. And it doesn't get past the issue that the thief/finder just needs to press and hold the power button and slide to turn off. Then turn it on later long enough to wipe it and restore as new. Either way, find my iPhone will have been completely negated, so why bother with restricting wifi or cellular data settings? I just see no gain to Apple even paying their iOS developers to bother implementing it.
Just my opinion, but some things are just not worth bothering about, and in this case I think that applies. The inherent limitations of the find feature just make it pointless (they even caught some kids in NYC who had foil pouches in their pockets, the heavy guage kind for long term food storage use, for dropping stolen iPhone's, Blackberrys and others into to block cell reception until they could take them out somewhere with no signal and ransack them). Its just so easy to defeat a network based location system that it gets silly trying to protect it's functions when many simple ways to defeat it will always exist.
Just my way of saying I don't think it was an oversight by Apple at all. I think they just deliberately ignored it as it there was no gain to implementing any such restrictions.