The reason why they aren’t being used is because they aren’t useful. Once they start making them useful them people will start using them more.I am surprised to hear people would seriously consider switching platforms due to Google's assistant potentially being better than Siri. Personally, voice assistants are a current fad that will fade over time. I see people eventually wanting less and less interaction with technology and automation becoming much more useful. I am sure Google has some advantages here also, but certainly no reason to switch platforms. Once Apple isn't the best overall option when it comes to performance, security, privacy, apps, ecosystem, and support, I'll consider switching. Voice assistants? Come on.
I really love Apple and I’m heavily invested in the Apple ecosystem but I also love technology. I really hope Apple have some good stuff up their sleeves for WWDC.