I didn't say we don't need sleep. I meant more that putting in some sort of effort that then requires sleep to compensate it is a decision our brain makes (or an adaptation it executes), more like putting debt on a credit card than putting fuel in a gas tank. Build up enough debt and you can go bankrupt (i.e. die), but never build up any debt at all and you'll be fine; you just won't have any of the things you could have that required that extra temporary liquidity/leverage to accomplish.

We could probably figure out a drug that would put us into a state where we don't need to sleep, ever--the resulting state just might not be something very much resembling "sentient human consciousness." It might not allow for memory-formation or System 2 analysis, for example, thus making you go through life only relying on the sort of "thinking" you do while dreaming. Animals that don't sleep, or that sleep very little (e.g. horses, at two hours per day) are also likely "stuck" in this state by design.

The real question is whether we could get anything productive done in this state, and that might be possible--it seems somewhat to resemble "flow."