1) The prompts/pipelines portain to proprietary IP that may or may not be allowed to be shown publically.
2) The prompts/pipelines are boring and/or embarrassing and showing them will dispel the myth that agentic coding is this mysterious magical process and open the people up to dunking.
For example in the case of #2, I recently published the prompts I used to create a terminal MIDI mixer (https://github.com/minimaxir/miditui/blob/main/agent_notes/P...) in the interest of transparency, but those prompts correctly indicate that I barely had an idea how MIDI mixing works and in hindsight I was surprised I didn't get harrassed for it. Given the contentious climate, I'm uncertain how often I will be open-sourcing my prompts going forward.
There's also the lessons on the recent shitstorms in the gaming industry, with Sandfall about Expedition 33's use of GenAI and Larian's comments on GenAI with concept art, where both received massive backlash because they were transparent in interviews about how GenAI was (inconsequentially) used. The most likely consequence of those incidents is that game developers are less likely on their development pipelines.
If your hand is good, throw it down and let the haters weep. If you scared to show your cards, you don't have a good hand and you're bluffing.