Should Speaker Manufactures provide a Frequency Response Graph?

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

Graphs and measurements can be important - but they are not the be all and end all.  I remember reading a long review on Audio Science Review Forum that gave an exhaustive analysis of a myriad of measurements and then made conclusions and recommendations based on those measurements.  Nowhere in the review did it mention how it sounded.  It left me scratching my head in wonderment.  

Imagine a restaurant review that tells you how the food was cooked and what it looked like, but never mentions how it tastes.

No.  But they should include a warning label stating that their sound can be highly addictive, thus straining relationships, creating an additional financial burden, and many hours of sitting in the "sweet spot" can be detrimental to your health.

I agree that one measurement (out of a possible 7?) does tell the whole story.  Horsepower and torque specs when selecting a automobile can be "useful".  But, we did reject a vehicle because we didn't like the cupholders.

If you go to the drag strip and test run your car and you post your 0-60 and 0-100 run, I wonder if you will get in trouble with the manufacturers.  And thus, the conversation.

@deep_333 +1

The most important graph for me is the Impedance & Phase vs frequency graph. I want to know if my amp needs to drive 2 ohm loads with a difficult phase angle. I believe it to be the most important data when choosing a power amp. next up is sensitivity. That too dictates my amp selection. Then I can vet by sound quality to my ears.