It’s not a physiological problem, it’s a technical problem. They do it so they work gets easier. It’s much easier to write code than to read code.
The fact that "write-only code" is apparently considered a part of sensible software-engineering practice speaks volumes about what their technical culture is like more generally. One would think that code should be much easier to read and survey than it was to write.
In fact, I'll often sketch out a block diagram or some pseudocode if I'm having trouble grokking something I'm reading just to help me get into the proper mindset. I agree this is a problem with the current state of the field, but I haven't seen any good solutions, only hacks and workarounds.
If the intention is for a uniquely skilled human to give a computer instructions, and the computer to execute them - then just write it in machine code.