Ruy Lopez

When I see GM's play Ruy lopez there is one set of moves that comes up time and time again.

1. e4    e5

2. Nf3  Nc6

3. Bb5  a6

4. Ba4  Nf6

5. 0-0  Be7

My question is:  Why not 5. ...  Nxe4?

Clearly there is a good reason  or GMs would do it.  Is it just that they'll be behind on development or is it a bad move in a way I can't see?

I believe because black couldn't hold the extra pawn after Re1, and white would gain some development in the exchange.

there is a variation after Nxe4, most gm's just don't like it, not because it's bad, because it's not thier taste...

5...Nxe4 is perfectly playable - it's called the Open Ruy Lopez ; just not trendy at the moment...

Ah.... thank you very much for your input chaps!