They pay for tangible "deliverables" from those professions, too, not pure thought and judgment. One could probably argue that, as with programming, one has to have written a lot of code in order to think in code at a higher level, so to speak, although I can't say to what extent that's true in each of those domains.

However, the first part applies to programmers, too. A lot of the value of code _was_ simply in the fact that it was written, so you don't have to write it yourself. I'm not suggesting there isn't more to the value proposition, but the value destruction is there.