The key is that HBO has always been a premium channel. That is, cable subscribers only got HBO if they agreed to an extra monthly fee.
ESPN and YES are part of the basic package for cable companies, which means that every single subscriber pays for the channel whether they watch it or not. That's actually a lot more lucrative. If YES tries to sell subscriptions around the cable monopoly, then the cable companies will just take them off the basic tier.
p.s. - I know that Discovery is basic cable, but they are an exception, and don't drive cable subscriptions the way sports does.
ESPN and YES are part of the basic package for cable companies, which means that every single subscriber pays for the channel whether they watch it or not. That's actually a lot more lucrative. If YES tries to sell subscriptions around the cable monopoly, then the cable companies will just take them off the basic tier.
p.s. - I know that Discovery is basic cable, but they are an exception, and don't drive cable subscriptions the way sports does.