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.
I can trivially buy a PDF from your online store, rip it, then claim you never delivered. Paypal specifically will nearly always side with the buyer.
As you might guess, that makes people selling digital products and services online very very sad.
Also, if you are a freelance artist, for instance, I could pay you with paypal P2P, then reverse the transaction after I receive your artistic work. Good luck proving act of delivery to Pain Pal.
2) Paypal specifically arbitrarily restricts countries to/from which transactions can be made. Since I am from [REDACTED], that sucks balls.
3) Fees for online payment systems (especially credit card ones) are relatively complex and high. Bitcoin fees are pretty low, especially if you don't need transaction to be confirmed ASAP
4) There are legitimate reasons to be unwilling to expose your personal information to some third party, for instance:
- some people happen to live in police states you know. Not the kind of police state Americans like to cry about, the "they check your documents on the street, ze horar, ze horar". The kind of where you get arrested and beaten (possibly to the death), then jailed (in case you were not beaten to the death) for running an unlicensed wifi AP
- After the Sony fiasco, even a legitimate customer of a legitimate business in a fluffy happy free country should think twice before exposing personal details to said business, especially so if the business is technically not subject to fluffy happy country's jurisdiction
5) Bitcoin is decentralized and thus quite resilient to local outages, be they due to State meddling, criminal agents, or natural events. That's a huge boon.