Why would you not move pawn two spaces during first move in chess?
Sometimes, center board control is not immediately the goal of a particular openings's strategy.  I'm referring specifically to two types, Larsen's Opening and regular Fianchetto openings.

Here, white is advancing each pawn only one square, 1.b3 or 1.g3.

As wikipedia states:


  The fianchetto is a staple of many "hypermodern" openings, whose
  philosophy is to delay direct occupation of the center with the plan
  of undermining and destroying the opponent's central outpost.


And regarding tactics:


  One of the major benefits of the fianchetto is that it often allows
  the fianchettoed bishop to become more active. Because the bishop is
  placed on a long diagonal (either h1-a8 or a1-h8), it controls a lot
  of squares and can become a powerful offensive weapon.


Regarding "regular" Fianchetto(vs long Fianchetto): Advancing the pawn two squares would deny it the protection from the rook's pawn and bishop's pawn.  Fianchetto would be a great  search term for finding openings making use of single-square pawn advancement.