The question is, does this matter?
Many really techy people - read that software developers and engineers- are taught a variety of "standard" development languages and toolsets that are currently known in the colleges and graduate schools, or which are provided by and used by their employers.
Otherwise all those languages and frameworks would have limited value. One of the best tests of market value is to browse the bookshelves at your favorite bookstore and compare them to the discount table (or that rack on the sidewalk outside) that contains all the "Fat Books" at a discount.
Now the cool and hip among you will ask, "Why are they buying and using Fat Books?" The simple answer is that the Fat Books contain amost of the technical information in one portable location. And if you've ever tried to solve a technical problem online, you'll get it.