Anyhow you don't get more exp because you fail and repeat the same leve, it's mostly because you link with many ppl who have the same leve. The point of abandoning is to make sure you and your group of static friends get the same leve again and you can link it again. Sometimes you don't even need to abandon it, the same leve will mostly likely pop again on counter soon enough, abandoning is just assuring you get it back on next reset. If there would be more variety of leves I'm sure there will be static ones just like Momodi's crafting leves which are there for eternity, so you would'nt even need to abandon any.