Why should you not sand grout?

Answer 1

Two answers here:

Grout should be sanded to add strength, just like you add rocks & gravel to cement to make concrete stronger.

Grout wears off a little every day & IF the flooring has

a very shiny surface, polished anything

is very soft, like sandstone, Travertine, Coral or marble

The sand in the grout is much harder than the stone & the released bits of sand from the grout will actually scar & scratch & dull the shiny polished surface as the traffic grinds it into the floor.

The installation of the wet, sanded grout can also start the delustering process.

Very narrow joint up to about 1/4" are usually considered to be safe to do without sand, but over that, an aggregate is needed & sand is the ideal.