h3/h6

Well yes it does.  It can be of great use sometimes to prevent a knight or bishop taking the g4/g5 square (main exception being the Fishing Pole Trap) but usually you have to think a) you are moving something forward in the area your opponent is attacking and therefore bringing it closer to his pieces, b) the pawn can never go backwards so you will never be able to undo the move if your defensive requirements change, c) by moving a pawn from h2 to h3 you weaken the g3 square which can be important for example if there is a bishop on c5 pinning the pawn at f2 against a king on g1 then a piece can enter g3 unmolested; another weakness from the pawn being at h3 is a knight at h5 exchanging for a bishop at g3 is normally okay for white if the pawn is on h2 as he can capture hg and open the rook's file rather than fg and rupture the pawns.  H3/h6 are not necessarily losing moves but there are lines where GMs play a piece out hoping for that move in response as they have drawn a weakness to attack.

Basically, it depends on the position. As you can see from the examples in Chernev's book, moves like this can often be fatal kingside weaknesses. But in many positions, controlling g4/g5 and giving the king some "luft" more than compensate for the potential weakness, especially in positions like the closed Ruy where Black isn't able to easily organize a kingside attack. As you gain experience you'll be better able to judge when such moves are weakening and when they are strong.