This is an excellent point. The reason why the opposite view seems to make sense with smartphones is because in the current state of affairs they are not design

This is an excellent point. The reason why the opposite view seems to make sense with smartphones is because in the current state of affairs they are not designed to be used without further manufacturer involvement (in fact they are actively designed to discourage any other party from acting like the manufacturer). But this is not a necessity, just the sad current state of the market, given consumers' present expectations.