Vince writes:

Are wall tiles normally not sealed, and just floor tiles?

I think "sealing" is a waste of time. It only lasts a few months, and you
are not going to be diligent in reapplying. Once you let it go, there's no
point in keeping it up.

Grout so-called "sealers" are a recent invention of the chain retailers
looking for a high-margin add-on. Places like Color Tile would practically
give away the tile to get you to buy an precious kit of installation tools
and supplies.