No grout okay?

I saw a tile floor with no grout the other day and it didn't look like there was anything wrong with it. Is that okay? Is grout just for looks just to frame the tile with a color that complements it?

No grout gives a place for dust, dirt and other gook to collect in plus the edges of the tiles are not supported. Tile has high compressive strength but little tensile or shear strength and the danger of chipping off an edge is increased. Put the grout in.

Terry:

If you don't have grout, then you'll have tight cracks around each tile. Now, what happens if you spill chicken soup all over your floor. It rots and starts to stink unless you can find a way to clean it out of them tight cracks around each tile. I can think of worse stuff to get stuck between those tiles if you decide to get a puppy.