“This must be a good idea — that's just what everyone does.”
What's happening
People use what others are doing as a shortcut for what's correct, especially under uncertainty — which works fine for picking a restaurant, but a financial decision being popular doesn't mean it fits your income, goals, or situation.
A financial example
Most people in a friend group lease a new car every three years, so it starts to feel like the normal, sensible thing to do — without anyone actually comparing what it costs against buying and keeping a car longer.
A better question
If nobody I knew was doing this, would it still make sense for my situation?