I assume a motivations of it are a) to have presence next to console games and b) gift-giving? If there were at least the basic versions of the games on the disc, you could add c) people with slow internet to the equation, but that seems less and less common.
This is part of why the grey market for keys has surged here - when Steam and the stores are both about the same amount for a new release, the only cheaper avenue is to exploit the real vs perceived forex difference, and (moreso) the fact that grey market key stores don't price in our consumer protection laws (and in turn, the buyer doesn't get any of those protections).
This is why I predict that the $10 per month unlimited video streaming services will work, and the $10 per month unlimited music streaming services will fail. I don't think enough people are prepared to pay that price for unlimited music.
(For reference: the launch price for all AAA releases is 2000 RUB (~35 USD), while the same games on consoles often go up to ~$60 and even beyond. Especially on the Switch: Zelda is ~$80!)
People here kinda grew up with the idea that paying money for non-physical things is just ridiculous. And still many people only pay money for multiplayer games that rely on official servers.
Steam offers the multiplayer AND good launch prices AND sales with huge discounts AND a very convenient interface for downloading and launching games… so tons of PC gamers did get sucked into it :D