In Philidor defense or in similar variations like the one above, If h2 is so horrible movement (it´s what the engines say, diving poor puntuation to this movement) why so many people do h2?

So many people do it (assuming you mean h3 or h6) because so many people are bad at chess.

GMs don't do it...

sorry I meant h3

Too many players fear pins, having been burned often and the others are afraid of doubled pawns.  Not sure how to create and then use opportunities they fall back on preventing their opponent's threats. They would rather not lose than not win. By failing to take an active stance they allow their opponents to take the fight to them and generally end up with a bad game.

People are too afraid of Bg4 once they know how a pin works. But it's really not worth wasting your time to prevent, it's not actually best in this position anyway.