It is hard to understand, indeed. Wolfram is clearly extremely accomplished by all standards.
We all know this. Why in the world does he pump all his written work with insufferable self-promotion?
Anyone in a position to make good use of Mathematica has heard of it. I haven't met anyone who doesn't know about WolframAlpha, and I've taught mathematics to high-schoolers.
Moreover, it should be obvious to Wolfram that his incessant self-promotion greatly reduces the probability that a reader will recommend his writing to their friends -- if Wolfram's goal is to promote his software, research, or even just himself, then he's clearly going about it in a ham-fisted way.