This view is too simplistic, because it does not take into account the dynamic forces acting on a slab. These forces must be taken into consideration when selecting the method of tile installation. Tile bonded to the slab. This method works fine as long as the slab is on or below grade. The problem with this installation is that tile bonded directly to the slab inherits all the problems of the slab.
Concrete slabs are subject to bending stresses, deflections, sags, creep, and cracking.
These forces will transmit directly to the tile resulting in loose or cracked tile. If new, the slab should be steel troweled with a fine broom finish. Although a wooden float finish provides good bonding they have been found to create other problems. If a surface treatment is needed, consider the types of treatment and the limitations of each. Acid etching provides a suitable surface, but cannot be used everywhere.