There is a lot of friction in using voice activated services. If I have a choice of typing "Weather in XXXXX zip" in the address bar vs. asking an assistant, I choose the former. Therefore, every time I use anything else but Google, I am afraid it won't recognize my command and I immediately feel like throwing that thing out of the window.
I need to be 100% sure that I will get a return on my time invested when it comes to searching or asking for information. When a Google search fails in a browser, at least I have something to bite on.
For other things such as timers, calendars, game scores, home lights, music - assistants are nice.