Unfortunately, I'm not sure that's actually as true as it should be.
Too few studio monitor companies provide comprehensive measurements. Neumann and Genelec actually seem to be the exception. Sure, you'll get a single on-axis graph with many studio monitors, which is better than nothing, but they're often smoothed to oblivion (see Presonus review) and there will be little to no information on directivity(again, see presonus), which in my book makes them all but irrelevant. Even in the pro world, it seems people would rather rely on hearsay, marketing, and subjective impressions...
Even with JBL Pro, you usually can't find the graphs right on its site. And personally, I'd like more information than a spin provides for pro usage, which is often more nearfield.