Apple music

I want to know why, with an Apple Music subscription, I am asked to pay for music on iTunes. Somebody answered on here that if you want to listen to previously purchased music, use the Apple Music app and iTunes for purchases. But that totally, (and stupidly) overlooks that if someone is paying an Apple Music subscription, they should be able to freely listen to music they haven’t individually purchased. That’s the whole point of an Apple Music subscription. Does anyone have any idea why I can’t listen to any song I want ON ITUNES with a subscription?