Licking is a manner of greeting for dogs. You’ll notice tail wagging, excitement accompanying it, and sometimes lots of jumping around.
In this greeting action, the associated emotion is love and affection. A biological reaction to this feeling is the release of dopamine and various endorphins that just feel good.
Puppies might instinctively pick up on emotional aspects of your behavior. Similarly, they might do the same when they themselves are feeling sad or lowly.
Humans cannot ignore being licked, so it’s a convenient coincidence that something pups love doing rewards them with something else they love — attention!
Here’s something you may feel awkward about. Humans generally taste good to dogs. Aside from your very unique scent and taste, puppies learn to understand their family members and environment this way, too.