But--most importantly--it's a retirement account that you can spend early, if you have to, if you have unexpected medical expenses (which is the main reason an otherwise financially responsible person would have unexpected expenses). And in that scenario it's a much appreciated buffer for needing to withdraw money from another retirement account.

But frankly, even if you are spending the money on medical expenses in the same year, you're also getting a lot of benefit out of spending pre-tax rather than post-tax money.