Frankly, it’s likely legal support. Amazon must give approval to Sonos before Sonos can move forward. And frequently, the delay between a service streaming in a country, and that service authorizing Sonos to stream can be lengthy. There are legal differences between the two, and often wending the way through each countries copyright laws, not to mention the rights originally purchased, can be tortuous. 

It would be a lovely world if there weren’t so many differing laws in each country regarding music streaming rights. And unfortunately, Sonos is at the tail end of all of this, and can’t add streaming to a country until such time as the streaming company gives them authorization to do so. 

For years services ran into legal problems getting Sonos support in Canada because Canada’s copyright/distribution laws considered multi-room audio to be multiple plays, whereas the US only counted the single stream coming into the system.  It could be something like that, because even today, most counties are still operating under copyright/distribution laws from the 1920s.