I don't think there's too much of an issue, I think it's just that sites want to be abl eto trust their payment source and cryptocurrency is pretty new - they like what ha salways worked for them...

I've bought things with bitcoin from places like scan.co.uk and they've been pretty good with everything. There's the additional problem with bitcoin in that returns aren't as easy to handle (imo) and transaction fees might have to be returned too a sther'es no RTS (return to sender) script in eveyr transaction that can be signed and returned to the previous owner for free too...