This is because Lynn does something that we see entirely too much of: imitating something that pleases her without understanding what she's doing while thinking that what's really just an option is an iron-clad law. Just as she draws hovercars because she thinks that there's no other way to show that a car is in motion, she ends her strips with her characters yelling like idiots because Sparky did it. What she doesn't understand is that there's a huge difference between Charlie Brown bellowing because Lucy made a sap of him and Elly hollering in blind rage because Mike wonders how long a lecture is going to last. In the first instance, we have a messed-up, gloomy eight year old thinking that the world is going to end because another screwed-up eight year old thinks it's funny and cute to be a malicious little shit. On the other, we have a tetchy bully hollering because someone she's dominating isn't cravenly grateful to be told what a disappointment he is and doesn't immediately agree that he owes her every penny she ever spent on him (as well as a rate of interest that would stagger a Mafia loan shark) because his need for attention and love was far too intolerate a burden for a thin-skinned narcissistic bitch like her to bear.
The problem, of course, is that Lynn believes that the joke is that two entitled, thin-skinned sourballs are embittered by the fact that other people insist on defying them which causes them to bellow at weak, powerless people for wanting to live on their own terms. It takes a special kind of angry, childish and clueless maniac to think that breathing fire at sitting ducks for not knuckling under quickly or cravenly enough to monstrously selfish people is at all humorous and it would seem that Lynn is that maniac.