Hi fiveAG
I understand your concern, but despite appearances Zom-B's answer should give the most straight-forward/accessible method. I'll try to add a few insights here.
Scientists do. Laboratories, universities.
Ideally, exporters should provide presets. Materials from the library are "advanced presets" because they provide eventually multiple textures to define materials parameters. The phong material has the option to use nkData wich addresses the issue straight away for many metals.
Now, what if we would want to do such a table for "wood" ? Crazy job, really. Wood colours range from green-ish to red colors (they are opposite colors !), and wether it is polished, varnished, weathered, closer to the core, or exterior of the tree, veiny or just grainy, "wood" would take very different parameters.
Under these conditions, all that can be done would be to provide approximate values or ponctual examples; that's what the library does
From there, it is more effective for artists to approximate the look they want using materials editors (standalone or from exporters).
Achieving realism doesn't come without a certain experience of the Indigo tools, a trained eye and basic knowledge of the real materials. That's a complex equation wich again is solved best, in my own opinion (and Zom-b's), by the material library.
Think of the material library as a super-table
That said, this Materials forum is the place to ask for a given case and most often this ends with a new material in the library !
This was long but hopefully explains a lot,
Cheers
