Its very common in loads of countrys - or at least terra-cotta tiles: Spain, Mexico, Italy, Greece. Its a good way to keep a house cool in summer.

terracotta tiles is a different matter from marble

Why? It occurs naturally in italy and some other country. Its just a material. One that is easily damaged by accidic cleaners, so not the luxery it sounds.

Marble ground down is even in toothpaste..

because marble is an expensive luxury and terracotta is not