I use multiple web browsers simultaneously (Brave, Vivaldi, Edge, Edge Insider, etc.), and it’s irritating to have to unlock my vault on each one individually. I get why the vault is locked when I close a browser, and for cases where I don’t also have the desktop app installed, this is definitely my preferred behavior.
But I do know that on at least some web browsers, extensions are allowed to communicate with native desktop applications. (For example, the MEGA extensions can have the MEGAsync desktop app handle downloads instead of doing it themselves. And the extension continues to inform the user of download progress.)
So, if a user has the Bitwarden desktop application installed, it would be useful to have the browser extensions rely on the desktop’s state for whether or not the vault is unlocked.