The reason that the button isn't on the lid is because that makes the lid uglier and, more importantly, undermines the philosophy behind the UI - which is to keep the device as absolutely simple as possible. The idea came from my partner (Zach Dunham) and was inspired partly by Radiolab's 2008 episode, "Choice" - it's a bit of a deep cut but I recommend listening to it and thinking a little bit about how choice functions in the FM radio world (which is, obviously, competing with Spotify & podcasts) today.
Also note that we developed the product in ~2013, when everyone in the hardware scene in NYC was all into IoT and making everything bluetooth. I think there was part of us that believed that IoT (and connecting everything to the internet) was misguided and that having a long term relationship with a local news/radio source (which for me is Hot 97, but for most of our customers is their local NPR affiliate) is actually really cool/powerful/valuable.
Lastly, you should note that a lot of our business now comes from selling The Public Radio to radio stations (again, mostly NPR affiliates) to give out as fund drive gifts. For obvious reasons, having a single-channel radio is attractive to both the station managers and their donating listeners.