Definitely not a dumb question. The newest Sonos speakers are Airplay 2 compatible, but mine are older and don't support it. You're right that I could've bought one new Sonos speaker to enable Airplay 2 for my whole system, but I'd always have to group that new speaker with older speaker(s) to use Airplay.

I could replace all my old Sonos gear with the new versions to solve that problem, but that's a pretty expensive proposition. The Sonos One and Zipp aren't that different in price ($200 vs $190), but the Zipp really competes with the $400 Sonos Move portable. And the Sonos Port (connects Sonos directly to a traditional amp) is ridiculously priced at $450, although I suppose I could just use the Airport Express if I'm not going to use the Sonos software.

The real reason, though, is that I don't want voice control and you can't get Sonos speakers that support Airplay 2 but don't have voice control. The Zipp also supports Bluetooth and line-in, so they're more flexible.

Edit: forgot that the Sonos Move also support Bluetooth (but that's their only device that does).