I'm happy with Wagerr so far, especially that the Mayweather/McGregor bet is already available. I also don't think they promised exchanges at ICO stage and I think they've suggested from early on that it suits them to be under the radar a bit for now.

However the answer to your question is 'As a courtesy to ICO investors, soon to be a requirement.'

ICO's which are rapidly added to decent exchanges relative to their size, have a high probability of maintaining and growing their value post ICO. ICO's which list on very small exchanges have a high probability of trading below their ICO price even if developmental progress is good.

So by not putting a tiny percentage of funds raised into centralised exchange listings, it's a bit like an FU to the people who funded you, because there's a high probability they will have made a bad investment timing wise, because the same shares will be purchasable at a later date, for lower risk and a lower price. So it's like 'Invest at this price in our ICO! (Even though we know it will be very likely be cheaper in two months due to our undisclosed exchange listing policy/strategy.)

As a result, I'm fairly certain more and more projects will actually need exchange agreements in place at ICO stage because investors will be more and more reluctant to invest, knowing that the biggest factor influencing their investment timing decision is whether or not the ICO will swiftly list on relatively large and liquid exchanges.