I don't get why it's even an issue to ban the other teams mains?

If I'm facing support mains, who only play support and are good with them, why would I go ban Yasuo? I'm cutting the legs from under the table. Cut their best champions and win. That is basic strategy. Also if they prolonged the game by making it some crazy kill numbers like 100 to 1, the other team does have a surrender option.