IEO is the right decision and the exchange is quite popular. I'll buy some tokens for me to just sell more in the future)
It is very important for exchanges to maintain their reputation, so they carefully choose projects for IEO and check their documents, especially large exchanges.
IEO costs money, as you need to pay the exchange to check all the documents, the subsequent listing of tokens and the IEO itself. Not all startups can afford IEO.
Cryptocurrency exchanges check the project, its founders. It takes a time and costs the money. Besides cryptocurrency exchange makes advertisement.