If tzizit are supposed to remind you of Hashem and the Mitzvoh whats the point of the tzizit in back? It's rare you see them at all even if you don't tuck them in.
We have two tzitzit in the front and two in the back; two on the right and two on the left. We are thus surrounded by the mitzvah of tzitzit. Since the blessing is "to be wrapped in tzitzit", we try to do as we say.
Orach Chayim 8:4.
One should have this intention in wrapping: That God commanded us to wrap ourselves in it in order to remember all of his commandments and to do them.
One should have two of the fringes in front, and two behind, in order to be surrounded by the commandments.