Why?

Why is that little ones are able to climb up on the couch before they can safely be on the couch alone? Why?
I feel like there is a period every day where I am bound to the couch so Eli can endlessly climb up, stretch as far as possible over the back of the couch, try to reach the lamp, fall/slide off the couch, and then back up again. And sometimes we skip the middle events, and it's just up and down continuously.
You would think this would make him tired enough to stay asleep while I lay him down for a nap, right? Well, you're crazy! Because apparently it doesn't make him tired enough to stay asleep for the transfer to bed! Again, why??