First off, this is a buzzfeed-level clickbait. I came here solely to tell you not to beg on the forums and then was genuinely surprised when your actual post was something at least slightly academic.
People beg, because it works. In part. People do give out free stuff.
People also beg, because they see other people doing it. They think that other people are doing it, because it works, even if it doesn’t really work all that well, and so they themselves do it.
It is kind of like cheat codes. If you can get ahead in the game by cheating, many people do. Getting items for free is a quick way to get ahead in the game. Many people think that begging is the way to go about doing that. Perhaps it is.