I'm not so sure — at least some arguments can be made for the value of time-shifting;
- In a browser's "reader" guise read later features seem quite appropriate and accepted (Reading List, Pocket)
- Snooze is now table-stakes for email apps (thanks to Mailbox), particularly in a work context ("I need to deal with this later" — rather than convert to task in another context, just bring the original back at a better time.)
- Web productivity apps may likewise be "things I want to deal with later" (Jira tickets, a training course, and shopping, entertainment etc out of work hours)
So it's true this can be accomplished via an extension, but TBH the UX quality of most extensions is pretty low (Tab Snooze excepted, but is it abandoned…?) so that's a relatively reasonable, but weak argument in favour of building snooze in.
Perhaps it gets more interesting combining Tab Groups and Snooze — i.e. I can setup a window/Tab Group of related activities/tasks and snooze the lot until later in the day, or tomorrow.
I keep open quite a number of windows tabs as "things I need to deal with soon", on the premise that out-of-sight-out-of-mind is a true risk when busy and subject to a lot of context switching. Those open windows/tabs are in effect the things I'm keeping on my desk (in the physical sense, i.e. my field of view) instead of 'filing away'.
But, just like one benefits mentally (mainly focus, but also low-level 'stress/anxiety') from minimising work-in-progress, I would value features that help me keep my "desk" clearer at any given time, while feeling "safe(r)" from possibly forgetting to get back to it at the right time.
…and of course the 'clear desk' / less open windows/tabs works helps reduce load — coupled with Low Power Mode it could really help free me of my office (powerpoint!)