It's a classic storytelling cliché that it's the villain who defines the hero, and nowhere is this more true in wrestling. If there's one thing that all fans can agree upon, it's that a clean, competitive match between two good, honest wrestlers is goddamn boring. We might like our babyface good guys, but the amount of pulse-pounding drama you can get out of liking something is limited. To really add the spice to the soup, you can't just cheer for your hero to win; you also want them to punish the dastardly bad guy.
Aristotle said that in tragedy, we purge the feelings of pity and fear, but in wrestling, the emotion we want to experience is a sense of justice. When we see heels cheat without recrimination from the referee, sneak away from fair fights, and laugh at the hero's indignation, our blood boils.
That's why when we're watching the payoff match of a feud, our desire to see the hero win is sometimes completely secondary to our need to see the villain get their comeuppance. And the absolute best heels are the ones who always seem to get away with their dirty tricks.