Why Are Openings Emphasized So Much?

Ok I get it. Openings are important. You obviously don't want to be blown out of the water before move fifteen. 

But I just have to shake my head when I see ten year olds trying to memorize* 25 moves in the Sicilian. That's ludicruous!

For most chessplayers, they would get the bang for their buck studying common middlegame themes or endgame positions. The way I see it, studying openings doesn't really become important until you reach 1800 elo. Before that, keep playing a set of moves that won't get you in trouble. No need to be fancy or aggressive--that's for the middlegame!

If you're starting out, here's my recommendation for an opening reportoire that won't take you too long to understand:

As White, 1. e4

• Against 1... e5, the Italian Game or the Vienna Game
  
• Against 1... c5, the closed sicilian
• Against 1... c6 or e6, the King's Indian Attack 

As Black, 

• Against 1. e4, 1... e5. Ruy Lopez, Italian Game, you name it.
• Against 1. d4, 1... d5. Queen's Gambit Declined
  

Against similar or slightly stronger opposition, the opening reportoire here will give you a good game (and you definitely will not be resigning before move 15). The opening suggestions are sound but if you know them well enough, you'll find that you'll have the edge.

*I want to emphasize memorize because I seriously doubt they understand the purpose of those moves.