The primary reason for getting a travel health insurance is to have a peace of mind that your medical expenses are covered in an event of an injury or unexpected sickness during your vacation in another country. when you go abroad, you will face uncertainty and your current insurances generally will not cover the risks associated with traveling overseas.
Travel Insurance is a necessity for elderly people, those who have medical conditions, or even healthy people that will be traveling to an underdeveloped region. If you are going to an underdeveloped region there are the risk of diseases, changes in the climate, the natural habitat, or unfamiliar microbe. Even in developed countries you can be exposed to outbreaks like what happened to California Disneyland which suffered a measles outbreak.
However, most travel insurance policies do not cover pandemics (flu outbreaks) but other providers do cover them so it is wise to check if they cover it before you purchase the policy.
If you have allergies or other preexisting conditions it is really important to bring with you your medical file from your personal doctor that describe the condition and the drugs you need. If you have a chronic disease, you will need to bring your prescribed drugs in the amount needed for the days spent in the other country.
Additional benefits of having a travel insurance besides for medical expense coverage, is it will also cover other losses that you may incur during a trip like missing luggage, flight cancellation at the last moment, travel agency or accommodation bankruptcy. It can also provide cancellation insurance by giving you full or partial refunds.
Stay safe and enjoy your vacation!