Apples and Oranges.
SketchUp is their product and helping users learn it is part of their product evangelism.
This is not universal however. Some companies do this free and some (like Rhino for example) charge for learning resources.
“Worthy” is the wrong word. It’s “being educated” enough to produce a working and stable extension.
There is no magic wand we can wave and make instant programmers. Sorry.
But all the Core Ruby and Standard Library docs are external. Any contextual courseware would constantly be referring to external documentation and reproducing what is already out there. At least for the basics of programming such as file I/O, iteration, reflection, etc.
And I wish Mr. Scarpino would update his book and release a new edition.
Yes many users who are very busy doing architecture may not have the time to get proficient.
Several of us have talked about starting a cookbook type of repository linked into the Files section of the Ruby API documentation.
A few of the Trimblers were interested at first, but then I got the feeling that their managers above them did not want to spend any company time (ie, money) on this expansion of the documentation.
So then we do have several (Julia and Thomas) who publish their own example repos and gists on their own time. Although beneficial, this also contributes to the spread (rather than the consolidation) of learning resources.
I attempted to bring some link lists together in the Ideas section of the Ruby Resources, but it could use expansion.