Dogs jump up at people to greet them. It starts when they are puppies. Young pups jump up and lick their mothers mouths to encourage her to regurgitate food and they will do this to us as well. So when your puppy excitably licks your face they are hoping you got food not that the are giving kisses!
Because they are generally a lot smaller than us we have a tendency to bend over to pet them, this only encourages more jumping up. As the the puppy grows older and gets bigger this jumping up behavior can become irritating and dangerous for those people unsteady on their feet.
This is when the dog does get pushed away and/or shouted at. People contine to push and shout for months or years with no reduction in the jumping . This only encourages the jumping. The dog is looking for attention and pushing it away is like getting petted. Even if you are shouting “OFF” or “DOWN” this is still interacting with the dog. Some resort to putting a knee up to catch the dog in the chest, this is very hard to do and is not very effective.
Other methods also involve pain or making the dog fearful like stepping on a paw or making a loud noise with a horn or shake can. These methods sometime will sometime have the effect of making the dog back away, now the dog is wary and does not trust you.
The best way to stop jumping up is to ignore the jumping and drop treats on the floor. This gets the dog to put his nose down to the floor and they soon learn that they might as well stay down as the food is going to appear on the floor. Only reward again if the dog puts all four paws on the floor,
For a dog that has been jumping up for a long time it can take a month or two for the behavior to disappear But it will work as the dog is not longer getting the attention Ignore the behavior you want to disappear and only reward things that you want to happen.