I'm a cat person so rarely have my kids licked me.
Note, I said rarely (not never).
Dogs are looking for food. When you come home did you notice they always try to lick your mouth? It's apparently an instinct in their genetic code or something. The parents come home and they try to see what you have brought them. It is supposed to stimulate the regurgitation reflex. Essentially, they want you to vomit your food into their mouths.