Bethesda is shutting down its Bethesda.net game launcher and directing its current users toward Steam instead.
A full timeline for the shutdown hasn't been announced as of yet, however the migration process is set to begin in "early April." Players who use the launcher to access their games on PC will have their accounts and "wallets" migrated to versions of Bethesda's games on Steam.
The sunsetting of this standalone launcher is another quiet notch on the belt for Valve and Steam. Publishers like Bethesda and Electronic Arts have spent some time trying to maintain their own PC fiefdoms for their games over the years, likely in order to avoid giving Steam or other external storefronts a cut of game purchases on PC.
A short announcement and FAQ from Bethesda doesn't dive into the reasoning behind the shutdown, but between Valve's concessions on revenue for top-selling games and the sheer size of the PC market, more large publishers have moved back toward the platform as of late. Even EA, who still operates its own launcher and PC game storefront, made waves a few years back by bringing its games and subscription library service to Steam.
Bethesda's games--including online titles like The Elder Scrolls Online--have also been available on Steam for some time.
Bethesda parent company (and Microsoft subsidiary) ZeniMax likely stands to make its operations a bit more efficient if it doesn't have to run its own online store, but does the closure of such marketplaces make Valve look a bit too strong by comparison? The U.S. Court system doesn't agree yet (and Valve has other third-party competitors like GOG.com and Humble), but it'll be worth keeping an eye on if other publishers follow Bethesda's lead.