This is especially true for Amazon, whose massive catalogue of products and services all but requires the speed available from reading and typing to navigate effectively.
Plus if you live with other people, voice interface use is disruptive.
It does occur to me that taking my shopping list on the phone to Tesco and putting things in a basket manually is probably not the future that Bezos had in mind for Alexa. But ultimately I don't trust Alexa / Amazon to actually do the buying.
This is an excellent point, and not only related to voice.
We often try to invent "smarter" ways to communicate, that are actually harder to use. Like having an app to control your toaster, which seems to be the next step, but simply having a physical device on it that takes 1 second to press is a lot faster, easier and feels more rewarding from the tactile feedback (I love pressing clicky buttons).
Voice is the same, turning up the volume on your TV is easier by simply pressing a button on the remote (assuming you have it in reach) than saying a voice command. This is also true in human interactions, sometimes it's easier and faster to just do something by yourself than having to ask someone to do that thing for you. Also, voice commands have to be perfect in the same way physical buttons are, whenever you press them the result is always the same. It's hard to keep using an unreliable input method, that has only 60% chances of doing what you expect.