I'd guess because you need a lot of data and a LOT of work to get anywhere close to where literally all competition is already. Even Besides Apple, Amazon and G

I'd guess because you need a lot of data and a LOT of work to get anywhere close to where literally all competition is already. Even Besides Apple, Amazon and Google no other company really has a decent voice assistant. Even Microsoft doesn't really manage to get up to the same level. Besides that, a voice assistant is never just a voice assistant. It's only useful if it already has a big range of services to integrate. Apple, Amazon and Google already had market-dominating services they could integrate to provide a decent starting point. You could see it in how each assistant evolved. Siri was always very much aimed at interacting with your phone. Messaging, playing music, local things. Things Apple already did well without a voice assistant. Alexa's main selling point at the start was it's integration with Amazon for shopping. It's still very important and probably the main reason I don't expect to get Alexa in Belgium any time soon since we don't even have an Amazon store. Google Now then couldn't really do much for you, but it's incredible at providing you with the right information, because it's powered by the world's biggest search engine (by quite a margin). Cortana for example doesn't really have any killer features, because Microsoft still doesn't have any market dominating services besides Windows (which doesn't really benefit from a voice assistant interface). So, in short, it's not about the voice assistant. It's about the ecosystem. And those are incredibly hard to build and probably impossible to open source.