Paypal is a payment gateway while bitcoin is meant to be a "invention" which later got a price tagged along. Anyway coming back to topic:
1) It has become simple for merchants to use bitcoin as a payment system due to emergence of services like BitPay .
2) BitCoin is used more often in trades rather than for buying things, it has still yet to catch up .
3) If "buyer's protection" was done it would be the same case as :
https://bitcointalk.org/index.php?topic=1195135.0 and you can see how so many people disagree on it. Bitcoin is a decentralized currency anyway, so its not possible.
I don't agree with this explanation or analogy.
PayPal acts as a payment intermediary and offers payment protection. I don't think a service like this exists that deals with bitcoin payments. The current system for bitcoin is no different than you selling your goods online for Dollars and facilitate the transactionson your own. If you don't want to use escrow you can require someone send you payment first and if you reneg they can hit you with a negative Trust rating on this site.