Don't see the reason why would they do that, this is just another altcoin, doesn't have anything to do with Bitcoin. Anyway, I got the feeling that majority of exchangers, at least those bigest and most important ones, will not support BCC. Could be a lot of confunsions before and shortly after August 1 until everything gets back to normal.
Same as always: Money. Most people lack any morals, they just want to make the most money. For Bittrex, this is just another opportunity to get traffic into their website and rack up trading fees, even if supporting Bitcoin Cash is bad because anything that supports a fork of BTC is bad in definition. But we can't do nothing about it. Let them host it.
Same for Kraken, these guys don't care, they just want the fees.
And im not saying that the rest of exchange have a moral standing about this. I guess that they concluded from a business POV that it is not profitable to list BCC for them.