Generally I think the issue is that there's a tension between your security vs Paypal's security (deliberate, motivated bad actors).
Maybe an analogy could be about using metal detectors as a layer to reduce bank robberies. A gun in a good guy's hands is a good thing to prevent robberies. Guns in a bad guy's hands are a bad thing to prevent robberies. Paypal knows you have a gun but they don't know if you're a good guy or a bad guy so it's easier to just ban guns.
Maybe an analogy could be about using metal detectors as a layer to reduce bank robberies. A gun in a good guy's hands is a good thing to prevent robberies. Guns in a bad guy's hands are a bad thing to prevent robberies. Paypal knows you have a gun but they don't know if you're a good guy or a bad guy so it's easier to just ban guns.