Haven't it occurred to you that the exchange listing also has some strategy to it, and perhaps the team wanted to settle other after-ICO matters (bounties, etc.) first before enlisting on exchanges?
If they wanted to wait then why release tokens at all?
Why not wait until they had an exchange and then distribute tokens?

Because then everyone would be jumping on them why they haven't distributed the tokens yet. You can't always please everyone on demand. A little patience is usually needed in life.