Yes, though it's increasingly rare because most game developers would rather just integrate with Steam than setup their own account and payment systems ... and I can hardly blame them.
A prime example is Andrew Gower's new game. The dude started Jagex and RuneScape he surely could make a new account system, billing system, etc for Brighter Shores ... he has all the experience necessary at a scale few developers have the experience with. He's just opting not to and it's surely because Steam's offering in terms of game promotion and ease of access is unparalleled.