You don't HAVE to do cardio, but I'd rather do some cardio and get to eat more. I only do cardio 4x a week usually for 30 min, and I enjoy it. Some cardio is good for your heart. Cardio doesn't have to be on a machine in the gym.
Too much cardio is bad for fat loss because it's catabolic. I definitely wouldn't enjoy it if I did those long grueling sessions day after day like I see some people doing. Most of these same people never lift weights either, and they look like shit. Even though some are skinny, it's that loose skinnyfat look.