Well, let's see...
1) first and foremost, reversible transactions open up a wonderful new world of petty fraud, especially for companies selling digital, ephemeral products (such as ebooks, or software, or online services) because delivery of those is problematic to prove outside some pretty in-depth interpol investigation.
Right. And with Bitcoin if someone steals my wallet and spends all the coins in it I'm screwed. No recourse. All my money is gone. With Credit cards I'm not liable and all my money is still there.
See what I did there? Still have money in the bank.