The Verge wrote about the Mac startup chime coming back in the new version (11! not 10.x) of macOS:
Apple is bringing back the Mac’s iconic startup chime in macOS Big Sur. The company hinted it might return by playing the chime very prominently during yesterday’s Worldwide Developers Conference keynote, and people who have installed the first Big Sur developer beta have reported that it’s back.
The startup chime was first removed from Macs in 2016 with the redesigned MacBook Pros released that year, and Macs released since then (with the exception of the 2017 13-inch MacBook Air) didn’t play the chime when you turned them on.
I would guess removing the chime was a Jony Ive decision (along with the keyboard and the obsession with thin devices with small batteries). It looks like a lot of things Apple has been doing lately are about undoing those choices. And the whole product line seems better for it.