When the barrier of entry is lower, people are more willing to go for it and not be turned away. Just as a product should be simple and easy to use, so should the payment be.
Things like too many option, requiring a completely filled out account or having to do other things before they can pay are barriers that should be avoided.
This might also be part of decision fatigue.
Reference
Ferriss, Timothy. The 4-Hour Workweek: Escape 9-5, Live Anywhere, and Join the New Rich. Expanded and Updated ed., 1st revised ed, Crown Publishers, 2009.
Highlights or timestamps
Second, you should make it as easy as possible for customers to decide to purchase your product. Don’t make them choose between a ton of options. The more colors and designs your customers have to choose between, the more likely they’ll be not to buy your product, because comparing all the options is exhausting.
— ^484b9e from The 4-Hour Workweek