Tiles are flexible and can be lain on most flat surfaces, but just because they can lie somewhere doesn’t mean that they belong there. Porcelain tiles are fundamentally much stronger than ceramic tiles, they are much better at handling footfall and environmental stress than ceramic tiles. Therefore they are much more suited to be on the floor, especially in high traffic areas such as the kitchen. In contrast, ceramic tiles are much weaker but it’s easier to create designs for them in the manufacturing process compared to porcelain, therefore typically it’s better to have ceramic on the walls so its designs can be seen and it doesn’t need to handle the stress of high traffic.
If you were to lay ceramic tiles in a high traffic area they will most likely crack, leaving gaps and making the surrounding tiles more vulnerable to cracking as well. It can end up quite a costly mistake if you have to replace multiple tiles and relay them.