Just as the popularity of IEOs is soaring many small exchanges are also launching IEOs services to new project so that they can also mint money easily. The graph which you have shown is for the big & top 20 exchanges & frequency of IEOs conducted in particular months also varies. The investors who are investing with long term goal are only making losses and short term investors are dumping tokens taking profit when they launch on exchange for trading. IEOs are still popular method to raise funds & a lot of new projects are adopting this method.