SEX IS AWESOME.. for the most part. Sometimes you're stuck with a bad partner, and you're just like “eh”. But your reaction isn't to never have sex again, because you know it will get better.
But some people just aren't all that into sex. Truth be told, this is pretty common. A lot of the time it has to do with hormones or medication, things that would chemically lower someones libido. But sometimes it comes down to attraction, and you just have no desire to bang the person you're with anymore. If that's the case, TIME TO BOUNCE.
So if your partner just isn't into sex and has no desire to ever have it again, it's time to figure out wtf is up. If you're married or in a serious relationship, seek help, whether that be a doctor or marriage counseling. Just figure out what's going on, 'cause although it's common, it's really not normal.