From the Help pages:
What is voting up?
Voting up is how the community indicates which questions and answers are most useful and appropriate.
When should I vote up?
Whenever you encounter a question, answer or comment that you feel is especially useful, vote it up!
Instead, it often happens that upvotes are used in the same way as a "like" on a social network.
Which are, in your opinion, the main reasons for such behavior?
In my own answers to this question, there are the ones I think are the most common, but, of course, you can add any other suggestions.
You can upvote for more than one answer to this post.
Please read all the answers before voting, don't stop at the first ones!
Edit: to clarify, for "wrong" I intend "not in line with what written on the Help pages".
The poll results will be used by Herr Professor Paulinho van Duck in his third article on the TUGBoat (the second is already in press). He reserves the right not to include an answer in his research because of moral scruples.