Why is Amazon credit the main form of payment?

There are many people that do not like Amazon, for various reasons. I personally am not fond of the CEO Jeff Bezos nor the price gouging you witness often, as well as the issue of fake reviews, fake products sold by 3rd party sellers, and the harm it does to smaller businesses. I would much rather prefer payment through Paypal or Venmo, even physical Visa gift cards so I'm not just limited to purchasing off 1 website. Many items I buy online are cheaper to purchase at Target.com or other retailers as Amazon no longer has competitive pricing. So I've always wondered why it seems that 99% of groups opt for Amazon payment when it may not be what the participants would prefer as compensation. I think the users/contributors to all these studies should have a bigger say in what they'd prefer as compensation for their time and effort.