You're completely right, however, to address these issues is EXPENSIVE. It requires hiring a lot of very skilled workers, who demand high salaries and it requires a lot of time. For a corporation, it is more economical to simply restrict traffic in ways which reduce strain on their network, rather than improving their network.
I don't even mean this in a bitter way. They're behaving as responsible corporations by delivering the highest profits possible to their investors.It's just that this doesn't always overlap with providing the best goods and services to the customers.