Having played with the Alexa and Google home. My take on why there are no hits is that it's very clunky to invoke apps, especially for one-off queries.
"Hey, Alexa/Google, Ask <keyword> to do <blah>" or some variation on that. Starting an app and then interacting with it works fine for some use cases but not all.
It really needs to be a flow of install app for given type of task, say searching for a hotel, and then like Android, there are defaults. So I say "hey alexa, find me a hotel room in blah" and it just knows to hand off to whatever my favourite is.
So long as all the core easy commands are only accessible to Google/Amazon, this is going to continue to be a problem.