There are many variations on a joke the goes like this:
A physicist, engineer, and mathematician are each captured by Omega and placed in sealed rooms with canned food, but no can openers. The physicist sketches the can and derives where the weakest point is, strikes the can, and opens it. The engineer looks up the weak points of the can in a table of cans, strikes it at the appropriate place, and opens it. The mathematician is found later, nearly starved, mumbling "assume the can is open!"
Suggesting "Why don't you just leave" is like suggesting "assume the can is open." The problem is getting to a point where leaving is viable (mentally, emotionally, etc.).
I don't mean to say it's impossible to "get it," but that you, me, and most counselors who are in a situation to professionally assist people probably don't.
The situation with abusive relationships is not analogous to the joke because it is not obvious to people who ask, why there would be such barriers to leaving a relationship (i.e. why such an assumption would be unjustifiable). People who ask "why don't you leave" are typically not aware of the usual barriers, nor do they have any reason to be aware of those barriers.
Furthermore, the question often comes up in cases where one party did leave, but kept coming back. So no, I don't see how the joke is helpful or how it shows poor assumptions.
Sometimes in an argument, an older opponent might claim that perhaps as I grow older, my opinions will change, or that I'll come around on the topic. Implicit in this claim is the assumption that age or quantity of experience is a proxy for legitimate authority. In and of itself, such "life experience" is necessary for an informed rational worldview, but it is not sufficient.
The claim that more "life experience" will completely reverse an opinion indicates that the person making such a claim believes that opinions from others are based primarily on accumulating anecdotes, perhaps derived from extensive availability bias. It actually is a pretty decent assumption that other people aren't Bayesian, because for the most part, they aren't. Many can confirm this, including Haidt, Kahneman, and Tversky.
When an opponent appeals to more "life experience," it's a last resort, and it's a conversation halter. This tactic is used when an opponent is cornered. The claim is nearly an outright acknowledgment of moving to exit the realm of rational debate. Why stick to rational discourse when you can shift to trading anecdotes? It levels the playing field, because anecdotes, while Bayesian evidence, are easily abused, especially for complex moral, social, and political claims. As rhetoric, this is frustratingly effective, but it's logically rude.
Although it might be rude and rhetorically weak, it would be authoritatively appropriate for a Bayesian to be condescending to a non-Bayesian in an argument. Conversely, it can be downright maddening for a non-Bayesian to be condescending to a Bayesian, because the non-Bayesian lacks the epistemological authority to warrant such condescension. E.T. Jaynes wrote in Probability Theory about the arrogance of the uninformed, "The semiliterate on the next bar stool will tell you with absolute, arrogant assurance just how to solve the world's problems; while the scholar who has spent a lifetime studying their causes is not at all sure how to do this."