Just guessing. The phone is ear-marked for a target market, e.g. Africa. If it connects to an American network without roaming and without ever having been to Africa, it's clear that the phone was not sold through 'official' distribution channels.
Some manufacturers require a 5 min phone call in the market where you bought the phone... Easy to meet for someone in the target market, but makes it hard to import a brand new phone from elsewhere. You could still buy used, but this is less attractive.