It is only obvious to people that do not think things through. When six people buy insurance, only six people are covered. When 100 people buy insurance, 100 people have to be covered.
The people already buying insurance generally have assets they stand to lose. The people that go without insurance, often do not.
Right now, you pay the money and get the travel insurance. You (apparently) want to compel people to provide a lot of personal information that the insurance company has to verify, which would take weeks and add cost.