Don't give them ideas.
Audio ads on amazon echo devices would be kinda funny though. "Alexa, wake me up in half an hour" - "I've set an alarm" … 30 minutes later … "*peem-poom* we would like to interrupt your afternoon nap for an important announcement from today's sponsor snoozeright™! Get your personal snoozeright™ pillow now for 10% off by saying 'alright i want one' right now. *peem-poom*"