Here's how it works:
1) You get hurt
2) You or someone else immediately contacts the insurer to report the injury and need to use the insurance
3) The insurer authorizes you to seek a medical diagnosis depending on the nature of the injury.
4) The insurer immediately starts looking for a reason to deny you coverage (Post claim underwriting)
5) You see a doctor who probably asks for payment in advance at least initially.
6) You report the diagnosis to the insurer and they either say sorry we can't help, or we'll cover you.
7) You ask if you have to pay first or if they, the insurer, will pay directly
8) They answer your question and tell you to return home as soon as possible for further treatment.
Not all travel insurance policies are a waste of time and money, but many are. Most policies contain lots exclusions, conditions and many ways to disqualify someone from coverage. Most polices are not really activated until you call and report a claim. Fail to notify the insurer quickly enough and that may be enough of a reason to deny payment. If you are covered, they will pay to get you stable and then insist that you return home for follow up treatment. Most policies will reimburse for an earlier flight home. Most policies do not cover you when you engage in "risky" activities, like drinking too much, climbing waterfalls, paragliding or hanging out at the car wash etc.
Plan to have a means to pay for medical treatment without insurance if needed. Read the actual policy which is usually available to be downloaded from a website somewhere. Otherwise call and ask for a copy of the policy. The sales pitch to convince you to purchase a policy never contains all of the exclusions and limits. Do not assume that because you have paid, you will be covered. Be very, very careful if asked to fill out a medical questionnaire when purchasing travel Health insurance. Eg. If there is a question asking if you have undergone tests for a heart condition in the last two years, and your doctor has taken your blood pressure, the answer to the question is then YES.
If travel insurance for you is limited to trip cancellation, delay and lost luggage, there are also a whole set of conditions that will not be covered. Buyer beware.