Sales are now normal in digital video game stores, but Steam sales have kept a special appeal even after many years. According to Valve founder Gabe Newell, the reason is not only because of the discounts themselves, but because Steam turned buying video games into a form of entertainment. In an old interview with PC Gamer from the time when Steam was mainly competing with the PlayStation 3 and Xbox 360 ecosystems, Newell explained that one of the platform’s biggest successes was its system of seasonal offers. Gabe Newell Reveals the Real Reason Behind Steam’s Success He explained (thanks GamesRadar),
Sales are basically dynamic pricing that let’s you to fully distribute your product to all available markets and with digital products sales hardly devalue the product making it a perfect strategy.
Yep. And also, they add a time pressure, so while gradually decreasing prices allow everyone to decide “ok it’s got to the point where I’ll buy it”, sales make you think “what if it’s more expensive for the next two years?” So you buy just in case.