Why don't speaker mfg list amps and associated equip they use to " voice " their sound?

Plenty of speaker cos. have branched into amps - Quad to Sanders.
Not so much vice versa - PS Audio

This is where "expert" advice (magazine, internet reviews, dealer advice, etc.) and 30 day trials come in.  I agree, though, that suggestions or recommendations from a manufacturer concerning match-ups would be worth considering.  The recommendation wouldn't necessarily be exclusionary, either.  The manufacturer could easily hedge their bet by saying that any quality component would be fine, but that Blah-Blah-Blah components would be exceptionally wonderful.

It could be limiting and it also means you are endorsing another brand that you may or may not have a relationship with.  

I do offer guidance and examples of brands that work well with my speakers.  Obviously I am going to be biased towards brands I carry but it does help with inference.  The unfortunate part though is that it is reflective of my taste. Looking at many systems out there, lots of people like extremely bright setups so I may be doing myself and injustice.  

This is not good for sales.HELLO!!!!

I’m sure a lot of manufacturers use more than one set of electronics to evaluate their speakers. That being said, they could be more honest about their speakers
specs. They never give exact numbers  regarding impedance. Also, I’ve never seen a spec regarding phase angle. Impedance and phase angle are so important in determining what amp will work best with a given speaker.