The reason is mostly because of the choice of payment processors that I think are clearly more encouraging people to buy.
Most e-commerce providers have PayPal/Amazon/Google Checkout available as payment processors, and also without the need for the customer to input all their data when they opt for them.
Services like BMT also allow for a simple credit card use, which is around 40% of our sales. Humble makes it possible through PayPal. But from my experience, most customers who don't have a PayPal account won't even click it to see if they can make the purchase anyway.
There are also some other drawbacks. Like the lack of affiliates and split-pay, and the necessity to send builds to Humble rather than upload them yourself (sucks if you need to make a quick bug fix).
The main draws, and those are pretty significant draws, are:
- Flat 5% with no minimum charge. BMT takes 9.5% and $1.25 minimum. It's a big difference, especially with cheaper games.
- Humble uses a neat little widget that's a part of your website instead of a separate webstore on the e-commerce provider's domain.