Do all hospitals and doctors in the USA accept travel insurance?

I know that different doctors and hospitals work with varying number of insurance companies. However, I haven't seen any doctor or hospital listing that they accept any traveler insurance plans. Does it mean that most travel insurance are not accepted by any business? What are they good for then?

EDIT:

After reading the answer, I searched for the policy with fresh eyes. Here is a screenshot which explains the insurance mess: : Disclaimer: I have no stakes in this business.