When is a3/h3/a6/h6 a good move?

I another post I asked about 3 ... h6 in an Italian game. We established it was concidered a bad move which was what I expected. 

Now, when analysing some of my positions, I notice that Fritz and Stockfish are recommending moves like a3/h6/a6/h6 rather early in the game. Around move 7 or 10 or so. 

I'm trying to understand the idea behind these moves during an opening. Normally every move develops a piece, increases pressure on centre squares or attacks other pawns/pieces. 

The moves in question don't really seem to accomplish anything from the above. 

Can someone explain the reasoning behind these moves?

You might like this series of videos. The first couple deal some with these moves: https://www.youtube.com/watch?v=l_zWJHYWWJs

Dan Heisman: Guide to pawn to rook 3.

https://webcast.chessclub.com/icc/c/Heisman/2010_03_06/Heisman.html

All depends on the opening, but there is an idea behind moves like this.  Unless you play The Andersen Opening 1.a3

A couple examples are:

Ruy Lopez: Morphy Defence, 3...a6, which "puts the question" to the white bishop. The main point to 3...a6 is that after the common retreat 4.Ba4, Black will have the possibility of breaking the eventual pin on his queen's knight by playing ...b5.

Sicilian: Najdorf Variation is Black's most popular system in the Sicilian Defence. Najdorf's intention with 5...a6 was to prepare ...e5 on the next move to gain space in the center