I think Amazon is the main one being talked about. Alexa was created with the thought that people would use it to order more stuff, they didn’t. They even gave away the Amazon Dash for free, thinking it would be the Alexa for the kitchen that would get people to order food, it had a barcode scanner. Amazon items and prices are too inconsistent for anyone to order anything with a voice assistant and they never solved for this. They’d need to end the entire 3rd party seller program to even have a shot.

Siri is more of a value add for people buying Apple hardware, like everything else in iOS and macOS. It can also be seen as an accessibility feature. It was never really meant to be its own revenue stream. It’s funded by hardware sales.