there is another possible, more charitable explanation for the wait period for device unlocking: as a cooldown period to help people avoid being scammed into unlocking their phones
I don't think so. OTOH what GP described (reseller earn money by batch unlocking phone and pre-installing not uninstall-able apps/malwares before selling to consumers) is very common some time ago.
True about uninstallable for cheap phones at least eg. Boost mobile phone <= $150 from my experience. I've seen notification I can't swipe close, the voice mail app having built in ads...
