Re: This is why I laugh at the hype around Echo, Alexa and Apple's new device
The assistant CAN be impartial, it just needs a written policy where it doesn't accept money from anyone to influence its decisions. You might not trust the review of a PC from a web site that takes advertisements from Dell, Microsoft and Intel, but you can probably trust the review of a PC from Consumer Reports, who accepts no advertising.
Given that Amazon makes its money from selling stuff, Google makes its money from selling you, and Apple makes its money selling you hardware, they're probably the most likely to adopt this stance - though it may still direct you to the Apple Store to buy a new iPhone even if you could save $10 getting it from Target.
But today the assistants are too stupid to do anything like what I want, so I can't say "I want an Galaxy S8, buy the cheapest one you can find". I could ask Alexa to buy it, but it would have to be from Amazon, and I doubt it would go through the third party affiliate stores. I doubt Google can do it at all - maybe there's a handful of stores it would support but I'd have to name it. Pretty sure Apple's couldn't buy a Samsung phone for you, though it might be fun to ask just to see if Siri tries to talk you out of it :)