The crew of Serenity has a lot of troubles and tribulations stacked up against them, but they know that whatever power in the ‘verse (including but not limited to Reavers) they go up against, they have the skills of the good Doctor Simon in the event that they run into health issues — such as bullets. Access to a doctor rightaway is a luxury that not everyone has, however, unless you’ve got one nestled away on your ship to patch you up after a good old fashioned firefight. Insurance helps you to better be able to keep yourself healthy even if your ship has taken a few bruises.
What made Mal and company seek out all manner of jobs across the ‘verse? Nearly every time they were looking for a guarantee — a guarantee that with the job done, they’d have pay in their pocket. A guarantee is exactly what you get with an insurance plan in the event that come down with a disease, have an auto accident, or need to go on disability because you cannot work. Health insurance plans give you value for your spending, even if you’re a smoker or have a pre-existing condition, that’s worth more than all the Companions on Persephone.