Dominance is an often misunderstood word I think.
I mean by dominance;control, hierarchical ranking, upper level, decision-making, order. And not humiliation or oppression.

licking can be a sign of submission - which in a dog can also mean comfort and "affection" to some extent - like the pups (or a lot of other young animals to that extent) like their mother's mouth for food, the dog is thus 'telling' us that he is like a pup, harmless. (usually goes with hears backwards and body made to appear small)

It can also be a dominance thing - the mother licks her pups to groom them and in that process she controls them - if they dont like it they will still get groomed - a dog doing the same thing to their owner is saying that basically he is the "mother" and controls the owner. A dog that does that will usually lick quite obsessively and growl at signs of the human withdrawing from it - a dog doing that would most likely stand over the owner in a confident posture - I would say its certainly not the most common explanation

of course it can also be something "created" by the owners - if they give attention/affection when the dog licks the dog will learn it as a way to get his owners attention - or if the owner trains the dog to lick ..

Anyway those are behaviourists' theories I tend to agree with but other behaviourists may have different ideas maybe.