In the U.S., one reason might be Federal Reserve regulation T, specifically the part regarding margin trading.

A credit card company extending you credit that is used to buy stocks would effectively be giving you a margin account and that has certain regulations including Regulation T.  So no credit card company will allow merchants to process charge transactions for funding brokerage accounts or to purchase equities.

Wouldn't the burden of proof be on the buyer at that point? Couldn't the seller just show delivery and signature confirmation?

With signed proof of delivery to the credit card billing address there is a good chance of successfully fighting a chargeback.

Banks will basically always rule with the customer.

The customer is their customer, and the bank makes money from their deposits, and the bank makes a great deal of money from the swipe fees and skimming off the top of every transaction.

A bank will not give you, a merchant, someone they care nothing about, an impartial review in most cases. They know that if they make you eat the loss there is no harm to them whatsoever. They know that if they make the customer eat the loss the customer will stop swiping the card, and may even move their money somewhere else.

And lastly, yes, I can buy a laptop from you, and then receive a laptop. I can then call my bank and say you shipped a phone book.

Why do they even believe a story like that? Because back in the days when PayPal had policies restricting chargebacks and things like that, those things happened. A LOT. I, personally, bought a hard drive on eBay and received a small brick. A friend of mine bought a computer and received a box filled with random junk that had about the same total weight, including a bag full of broken action figures!

yes -- most of the people who traded with the top 50 in this list would disagree that sellers have any decent chance of fighting a chargeback: http://bitcoin-otc.com/viewratings.php?sortby=neg_rating_recv_count&sortorder=DESC

That may be their opinion. But how many of them run an actual business? We do. And we win chargebacks. So from experience I can say that a signed proof of delivery goes a long way to fighting a chargeback.

its a huge target for fraud. Not only chargebacks but rampant use of stolen cc's would take place. I wouldn't expect to see anyone taking credit cards for BTC anytime soon if ever. The two just don't mix.

The future of crypto currency safety on chargebacks lies in a tool such as the blockexplorer. If when, where, and how much are decided in advance and made public or at least held by a trusted third party, then chargebacks can be fought because you can prove that you held up your end of the agreement.

Masons - One word answer, simple!
You control all banking, you control what people accept. Plain and simple.

We'll never see bitcoin fully integrated into the current system, because its the antithesis of the current slavery debt based fiat money system.

As long as people have to exchange their bitcoins for dollars, and banks are not going along, then bitcoins will only be alongside the current system, but it will never be fully integrated. Someone who accepts Mastercard today, will likely not be doing it tomorrow. Unfortunately.