Let's analyze the sign (from the television series Impractical Jokers). The sign (click to enlarge the image) is telling me not to stop doing something, in other words, to keep doing something. What am I doing? I'm letting people not help. This implies that I have the power or authority to stop people from helping, but am not exercising that power or authority. I'm being told to continue refraining from exercising my power or authority.
