The problem here is because of the lack of regulation around Bitcoin, not because Amazon is afraid of Bitcoin or because they are afraid of a lack of regulation, but this seems to be an Amazon case that is too big to adopt a product that can eventually fail.
this can't be the reason, at least not the only one or the biggest one.
simply because there are already other big companies that have adopted bitcoin. for example Microsoft has been accepting bitcoin payments for many years now! if there was any fear of lack of regulations then others would have also been worried.
other giants like Facebook, is exploring blockchain technology.
Facebook is not exploring blockchain technology. facebook is exploring ways of making more money from a hyped up situation. what they created is no different than a bank or any of the online processors such as Paypal.