The non-technical iOS users I know would never change a setting in Settings they do not understand (unless someone they trust, namely me, tells them to do it).
If that is not enough, the unlocking process can be as complicated as needed to discourage careless unlocking. Most people, when asked, e.g., to convert a decimal to a hexadecimal or to engage their frontal lobes in some other way, stop being careless.
Remember that the only point I'm trying to make is that it is not strictly necessary for Apple to do their best to keep motivated technical users from escaping their "jail" to prevent kids and grandmothers from harming themselves.
And does anyone actually believe that protecting naive users is the only reason Apple makes it as hard as possible to jailbreak iOS?
