The user should be the ultimate authority of what their computers do, not the app developer. It's my phone, not the app developer's phone. If my phone has a "screenshot" function, I expect to be able to invoke it whenever I want, not whenever some app developer deems it OK.
I hear your perspective. I am not particularly advocating either position. I am just pointing out that the alternative may be fewer apps available on one's favorite platform. Everything is tradeoffs, and fortunately one can always boot into an OS that will screenshot how you want.
