Does everyone really spend 7k * market gains on medical expenses? I'd be surprised if I've spent 1k in my life so far. (Keeping in mind im only 26)
$1k in 26 years? And you have had high deductible health insurance before? You are very lucky to be so healthy. Do you get a yearly physical? Take any medication? I think you must be underestimating your spendings...
I have a PPO, so most things are covered way more than they ever would be on a HDHP, but I easily hit $500-1,000 a year, and some years hit my out of pocket max of $3,000. Last year due to emergency out of network costs and stupid "allowable charges" BS on those out of network, my total spending was nearly $20k.
If you don't spend that amount in medical costs, you are basically either setting the money aside for a year in the future where your situation has changed and you spend a lot (for example, on a HDHP family plan with a $6,000 deductible and a $25k out of pocket max, and your child breaks their neck and spends a few weeks in the ICU, a few weeks in the hospital, a few weeks in inpatient therapy, a few months in outpatient therapy. That money is EASILY all gone. Been there, done that, except I was the child.) or you are waiting until you are 65 to access it, and it is just another investment account.