And also, previously: In the dark times when end-user wireless network bandwidth very low and glitchy (and most home users didn't care much), and before "mesh" became a term associated with a single-box collection of items that could be bought at Wal-Mart, Sonos devices were able to mesh together and form their own wireless network that Just Worked.
In software-land, they even solved latency inequalities well-enough to keep things properly in-phase at 20KHz between different devices, to allow stereo imaging to work correctly betwixt two wirelessly-connected speakers. (This seems very passe' in these modern enlightened times of seemingly-independent wireless Bluetooth earbuds, but it was a tough nut for them to crack back in 2002[!].)
It wasn't all smiles and rainbows, of course, because the world never properly settled on one, true, universal implementation of something like Spanning Tree Protocol and agreed on how to use it. It was very possible for a person to really hose up their network by connecting Sonos gear the "wrong" way -- by connecting "too much" of it directly to the LAN.
But those potential problems were broadly mitigable by picking exactly one Sonos device to bridge the wireless SonosNet into the home's LAN: Ideally, a Sonos Bridge would -- uh -- provide that bridge, but any random Sonos speaker (or subwoofer!) would do just as well. This worked, but it involved some aspect of wifi.
And yeah, the problems could also be mitigated in other ways if they showed up: A person could certainly plug in their Sonos sub, sound bar, and surround speakers into Ethernet -- which was really quite neat and tidy if it worked, and it often worked. But it was a pickle if it didn't work because STP implementations can be an unadjustable boondoggle in the consumer space.
They had a really neat and rather unique thing going for quite a long time before the market shifted to make their products apparently be fickle, outdated, inferior, and expensive. ("What, no Bluetooth?" people once said, even though, being an independent network-based streamer, it doesn't have Bluetooth problems like a person walking to the other side of the house with their phone where everyone but them can hear it noisily glitch out until they wander back.)
Nowadays, SonosNet seems to be mostly dead, and the STP problems died with it. Common home wifi has also grown up a lot since 2002. So a person can hard-wire their Sonos sub, soundbar, and surround speakers into the LAN without fear of badness -- or use one or more of those wirelessly, instead. All without problems.
> So a person can hard-wire their Sonos sub, soundbar, and surround speakers into the LAN without fear of badness -- or use one or more of those wirelessly, instead. All without problems.
Eh, I just had to go through and disconnect all ethernet from a bunch of Sonos devices in my house a couple months ago due to issues. It's on my list to go through and connect everything to the LAN when I get the time to make another couple ethernet drops - but mixing wifi/ethernet connected Sonos devices is not a great experience even in 2025.
Sonos has its issues, but I do need to point out that their subs (and the rest) all have Ethernet ports in addition to WiFi.