'Is it a normal practice ?' => It's pretty commun, a good part of the community just abandon regularly.
'How does this goes unpunished' => It doesn't. But hanabi isn't a game which give some trophies/ranking because it's easy to cheat by just telling in chat what you have.
'Does BGA encourage this kind of behaviour?' => You can always refuse an abandon, it's not like you was forced.
After, it's just a different goal for differents players: some of them want to finish all games, some only abandon if the game is really bad (many mistakes), and some abandon as soon there is a little mistake.
Some players just want to do 30: they don't all abandon for elo.
