I'm pretty sure Sonos is a "thing". Although you're not entirely sure, with the "probably a digital store" suggesting you've never used it. So you can say you learned something today, Sonos don't have a digital store to buy music, they let you use whichever supported service you already use.
The app? Well that's necessary as you're not streaming from your mobile device, you're instructing the speaker where to get music from. So I can start playing my Spotify tracks, leave the house, and someone else can pick up with their app and carry on. Try that on Bluetooth and you'll get 10m from the front door.
Whether it's your thing or not is down to you, but they've got a pretty good customer base so it's definitely a thing. You don't have to get all frumpy and old fashioned just because the word "app" scares you.