Before anyone goes off the deep end, please realize that PG's rankings use a point system, where points are awarded based on how highly ranked a given recruit is.
There is a flaw in this system, in that it rewards programs that recruit a lot of kids. Some programs only recruit a lot in years when they really need a lot. Others recruit a lot year after year and then cut players who're already there year after year, too.
If a program projects that it has only a handful of guys leaving at the end of the year, and if it is not one prone to cutting players already on the roster, then it may only recruit 5-7 guys in some years. With that number of recruits, you simply will not accumulate enough points to be listed among the top classes.
To answer the other question above, neither pitchers nor non-pitchers are weighted any differently just because of their positions. Though I think it's just a fact that by far, more of the top-ranked players are pitchers and more of the recruits are pitchers than any other position. But then again, most college rosters are at least 45% pitchers (or 2-way guys). So this is not a bias in the rankings, more a reflection of reality.