Should Speaker Manufactures provide a Frequency Response Graph?

They should at least make them available upon request. 

I have never been able to discern the voicing of a speaker from performance specs.

From manufacturer specs? That makes sense.
However, it is not difficult to do with thorough third-party measurements. It merely requires an understanding of how the measurements correlate to perceived sound quality. For example, take any two tweeters and provide a CSD/waterfall graph for each. Based on the graphs, I could tell you with certainty which one will sound cleaner and more refined.

Another example: a speaker with a wider horizontal dispersion over a large bandwidth will produce a bigger soundstage than one with a narrower dispersion over the same bandwidth.

“It merely requires an understanding of how the measurements correlate to perceived should quality“

Good luck with that.  A panel of listeners will rarely, if ever unanimously agree on the sound quality of a speaker or system.  On top of that, any speaker will sound different based on the room, the setup, the amps, the cables, the source, condition of the power coming into the system, etc.

“…take any two tweeters and provide a CSD/waterfall graph for each.  Based on the graphs, I could tell you with certainty…“. No, not with certainty.  You might guess right some of the time.

“… a speaker with a wider horizontal dispersion over a large bandwidth will produce a bigger soundstage than one with a narrower dispersion over the same bandwidth.“. Not really.  Careful, you are using lots of fancy terms here without context.

Have you actually designed and built a speaker?

@mijostyn 

”The amplitude response of a speaker is a moving target. It will change depending on the room. There are also other factors that play a significant role in audio fidelity like phase behavior and group delays. I do not pay attention to specs. I review the design of the speaker and make the best determination I can that I will be able to make the speaker perform to my expectations.”

“I might also add that measuring your system in place is much more informative.”

This is how I roll. However, when I was much younger, I was a technical specification person. If the device had low THD/IMD and depicted a ruler flat response, to me, it must be a good thing. As we grow and mature in this hobby, we now know through experience that that methodology is not entirely accurate as to what we actually perceive as musicality in the actual operating environment which has numerous variables. 
 

There is one caveat. When auditioning very large speakers, multiple listening samplings at various locations / venues must be conducted in order to grasp the persona of that speaker. When comparing and contrasting a speaker you have owned for many years to something different, it will be readily obvious that what you hear is either good or bad in a fairly short amount of time. That’s why when I go to audio shows and walk into a room, if it sounds bad to me, I am out in either a few seconds or a minute. My comparative reference is different than anyone else and what sounds good to me, may not necessarily sound good to someone else. 
 

What should start a new thread call titling it “What have you learned” or something like that. 

For what reason?  Are you going to buy because of the chart?

Great question @bigkidz ....The chart is more likely to cause me to avoid a particular speaker. If for example the speaker has a rising response due to lack of baffle step compensation....that's not for me. I know that speaker will sound too forward and possibly even shouty.