I am tiling my kitchen floor, and I have a question about sealing the tiles...

So, when I am sealing tile…

 The books and the people I ask at Home-Depot say that I need to seal the grout between the tiles, and that is all.  So, I bought this grout sealing tool that has a tiny brush and a reservoir for sealer.  But, I am thinking now, why not get extra sealer and use a paint roller and seal the whole floor, tile and all?

 My argument for this is that even though the tile is glazed, a coat of sealer on top of the tile can only help keep out moisture and cleaners that would break down the shine on the tile.  Ar there any arguments against this?

The sealer would not adhere well to the glazed tile, and it’s not necessary. It works well for the grout because the grout is porous, while the tile is not.