Is documentation a valid reason?

Old Linear Technology, Analog Devices, and Texas Instruments data sheets were and are fantastic. Someone with an understanding of little more than the fundamentals of resistors, inductors, and capacitors could learn about and implement a DC/DC converter from those docs - and the simplest ones are the oldest ones.

A seasoned electronics designer with previous examples to draw on can select an IC and basically reverse-engineer it from the sample application and comparisons with previous designs they're familiar with. If they get stuck, they will call their vendor...they might not even read the docs. Hobbyists can't do that.