Ovens have timers built into them to make sure nothing burns. Without a timer, life’s distractions can get in the way, and you could very easily end up with a blackened piece of brick, unrecognizable from what you were trying to cook in the first place.
This Reddit user purposefully didn’t set a timer when they put a cheesecake in the oven. It seems like it was one of those good ideas that stem from having too much confidence. They were roaming the infinite pages of Reddit, when, suddenly, they remembered their cheesecake. Let’s just say, they didn’t have edible cheesecake anymore (via Reddit).