As said already chargebacks are a key issue but there are two other issues, point/rewards programs & cash advances.
If you buy a bunch of BTC on your CC you're earning points/cash back depending on the cards reward program. Sell the BTC before price changes & you wind up with enough points for a free flight/cash back/other rewards.
Similar issue with cash advances. If you use a CC to buy BTC, sell the BTC for fiat, then pay back the CC at some point with that fiat, you preformed a cash advance without the bank being able to charge their ridiculous fees on it.
Unless an exchange is defrauding banks by lying about what the charges are for, customers cant avoid cash advance charges and interest. Any credit card purchase of BTC is definitely treated as a cash advance; Im not aware of any exchange that processes the charges more favorably. Thats not to say that fraud cant happen though. I remember back in 2010 or so when Pokerstars bank was processing poker deposits as purchases for golf balls, etc.
And if I could get cash back for BTC purchases, I definitely would. But no CC issuer pays out rewards for cash advances. Rather, they ream you on fees and interest. Last time I checked (last year), Bitstamp was charging 8% on top of spot prices when using credit card. Cash advance fees tack on another 3-5%. Who the hell is paying 10-15% above spot for the privilege of using credit cards? People charging back thats who. Not sure who is dumb enough to pay those prices otherwise.