If a teacher finds that every student answers a question wrong on the final exam, do they blame the students? Of course not - the most likely assumption is that the instruction didn't communicate or explore that concept well enough. What if only a single student is incorrect? The teacher can probably safely assume that there was no flaw in the presentation of the topic - it was at the appropriate level for the students, it was explained clearly with plenty of out-of-classroom reinforcement, office hours were provided, etc. - and they don't have to change their plans next year.
But science communicators aren't teaching in a formal setting. There are no exams or quizzes to judge our audiences, and the goal of our instruction is different. If a single person walks away from an educational moment not understanding the concept, we have to assume that it's entirely our fault.
That assumption may not always be true - maybe that person was browsing their social media feed or idly mulling over lunch options the whole time. But science communicators have an obligation to our communities, and part of that obligation is ensuring that everyone - everyone! - gets access to scientific facts and concepts. If we blame the audience for misunderstanding, we've failed our responsibilities. By putting the blame on ourselves, deserved or not, we empower ourselves to do something about it.
Why was that person so easily distracted? Did we not present the topic in a sufficiently compelling way? Did we not shape our approach to speak to that one specific mind and one specific heart, with that one specific background and life story? Did we not tune our presentation to the right educational level?
Let's assume that no, we didn't.
50% of the audience walks away understanding the concept? 90%? 99%? Not good enough. 100% is an idealistic and probably unobtainable goal, but by putting the responsibility on ourselves we create within us the opportunity to affect positive change in the world and the chance to share the story of science with audiences that need to hear it the most.