double jump... next step in evolution?

So I was thinking in class today - not about gendered communications, mind you - but about
the good ol' staple of platformers and various action/adventure game characters:
the Double Jump.

{Yes, that's Penny Arcade. Yes, I read it from time to time. No, I didn't have this in mind, nor
had I seen it, before I googled "double jump" to get an effective picture to add.
Cause we like pictures.}
Really, this perfectly illustrates what I was thinking. Now, in some games it makes sense.
Psychonauts gives you mental powers, and the double jump relates that - he has a little
mental bubble pop up underneath him. Castlevania gives you magic boots. Any game in space
gives you rocket boosters or rocket boots or whatever.
But why did developers decide this was so supa fresh? Was it to give their levels more space
within the constraints of not having a 3D world? Was it just to give their levels more
dimensional perspective?
I don't know. But I was trying to remember all the games that gave you double jump just
cause, and I really couldn't think of any, but I know they exist.
So, the question is this:
Do we still need the double jump? And if so, is it because we're just so used to having that as
an asset that games would be weird without it, or is it because developers don't feel like
making levels that are designed around using a well-timed single jump or box to crawl up on?
Really, it doesn't matter much. I never had a problem with the double jump, I was just bored
in class. Any thoughts?