The telcos were a national monopoly, which then became "deregulated" but for all practical purpose they hold a monopoly position with regards to cable-in-the-gr

The telcos were a national monopoly, which then became "deregulated" but for all practical purpose they hold a monopoly position with regards to cable-in-the-ground and various local right-of-way rights. So, the SMS solution is what these quasi-regulated entities gave you. Whereas iMessage, RCS, Signal, etc is what private industry gave you.