Your smart device is listening to you. But the company's running the apps arent.
Can you imagine 4billion active VoIP connections permanently open with Google, Amazon, insert random app here?
Your data usage would be through the roof, the company's would literally explode with denial of service overload etc.
Your mobile, Alexa etc has a simple subroutine LOCALLY running that listens for a key word. When it hears the word, it then has a second sub routine which says 'if words xyz are said, record the next and connect to ip address 1234.1234.1234 and run'
I work for a global IT company and we use the same Alexa driven routines for automation of server management and they DO NOT record everything. Ever. It cant
I have an android phone. So it has Google assistant, I also have Alexa mobile, Facebook video and a variety of different apps with mic access granted. Which one gets the mic if it's recording in the background? Or are you suggesting my phone has several open VoIP connections permanently enabled? In which case why is my data usage zero when I don't use my phone for a few hours?