Why is the engine frame-rate limited?

[bugmenot]

It's not about the speed; it's about the timing.

Imagine two clocks.

They're both ticking the same speed, 60 times a minute as clocks do.

Does this mean you can only hear a single tick each second?
Maybe, but it's more than likely that one is ticking a liitttttle bit later than the other.

VSync makes them both tick at the same time.