Why birds do not fall while sleeping

This article doesn't even try to address what I feel is the deeper and more interesting question (but probably one that can't be answered): Why is it that horses, cows, giraffes and birds have all had to come up with a purely passive solution of "locking" themselves in place, either via their joints (for the four-legged), or via the tendon mechanism described here for birds?

I.e. why wasn't in simpler in evolutionary terms to come up with some mechanism where 1% of the brain was dedicated to the relatively simple task of "station keeping", while the rest of the brain could benefit from sleep?

Also, why didn't any animal evolve a way to avoid sleep completely?

Sleep has crucial role in survival and well-being

Yeah but what role? 24h always at least a bit running brain has also crucial role in survival.

I get some form of maintenance is needed, but 8h every day seems like an overkill for very significant disadvantages. Many other mammals require significantly less sleep.