I see some confusion as to why anybody would want these devices in the houses whatsoever and would like to offer an answer:
Quadriplegia.
Imagine walking into your house one day and all of the keys had been taken off your keyboard, every light switch is smooth, all of the doorknobs have disappeared, the controls on your stereo have disappeared and every other switch, lever and/or physical method of interacting with your devices had disappeared. That was what it was like to be me as a quadriplegic Geek.
Then came the Amazon Echo and its ilk. The Echo coupled with Home Assistant[1] has absolutely revolutionised my life and enabled me to do all of the things above that I wasn't able to do before. It's a pretty compelling reason for me.
Am I worried about my privacy? Absolutely. Am I any more worried about the Amazon Echo than I am about the microphone in my iPhone, television, MacBook Pro, iMac and weirdly my fridge? Nope.
As others have pointed out it's a trade-off, I could be completely private and not be able to do anything or I could accept this somewhat Faustian bargain and be able to control almost every aspect of my house. Crappy situation to be in, but there is.
There are a few open source alternatives coming through which keep everything within the wire, but until they get traction enough to be out interact with all my other devices I can't use them. Which sucks.
Anyway, hopefully this comment was helpful and am available to answer questions on any topic other than physics. I'm rubbish at physics. :-)