Why does my dog lean on me?

Dogs are enormously tactile and they don't respect "personal space"
quite as much as people do. It's very common for dogs to get close to
people and lean against their legs. Our usual reaction is to reach
down to scratch their heads-which may not be the response they were
after at all. Dogs who merely lean, as opposed to a catlike rubbing
back and forth, may be attempting to expand their personal space by
taking over .yours. Conversely, some dogs lean as a way of expressing
affection and establishing possession, much as people put their arms
around each other when walking down the street. And sometimes, of
course, a lean just means your dog is a little itchy and is rubbing
against your legs to scratch a hard-to-reach spot.
humansocietyyukon.ca

Dogs that "lean into" their masters are displaying a form of aggression.

They have not been taught ( or choose to disassociate ) that their
master is the "alpha" animal in the household ( pack ).

These dogs frequently disobey their master's commands as the dogs feel
they are the "alpha" animals.

Hope this helps.

Steph53