Yes. Unless you are a millionaire. Medical treatment aboard, especially in the US, can be extremely expensive as can repatriation, especially if you need an air ambulance.
In a freak accident, 20 years ago,whilst in the Dominican Republic, I broke my leg in four places. Two operations, four seats on return plane for me to lie down and a limo to get me from the airport home was £10,000. That didn't include various incidentals like taxis, phone calls etc..
My dear old Mum had a heart attack while on holiday with me on Corfu. Chief doc at local clinic and heart specialist visited hotel every day. All paid for by insurance company.
If you can't afford the insurance premiums, DON'T GO. You may regret it.
I have a couple of medical conditions, neither serious, but have been quoted £700 for two weeks. Going on comparison sites I found a decent policy for £186. Shop around.