Requiring certain healthcare plans to access HSAs is the only thing that keeps HSAs from primarily being (in terms of amount of tax income lost to the program) a benefit for the upper-middle-class and higher, i.e. a regressive redistribution scheme.

Optimal (maximizing your benefit... and also cost in lost tax receipts) use of HSAs requires not touching the money until retirement. You pay medical bills with non-HSA money and keep the HSA money invested and growing tax-advantaged, like an extra retirement account. Spending the money you put in every year offers relatively tiny gains compared to keeping it in those accounts for decades.

Your options to mitigate this are to limit access, or to make it undesirable to keep money in them long-term, approaches to which look kinda FSA-like.

Even if you spend the money you put in to an HSA every year, you still saved the marginal income tax on that money, which is a lot better return than most other short-term "safe" ways you might save for unexpected expenses.

> to make it undesirable to keep money in them long-term

We could just continue to enforce the 20% penalty indefinitely to get rid of the concept of these accounts turning into retirement accounts.

FSAs benefit the upper-middle-class and wealthy more than poor people as well. You'll see quite a bit more savings when your top end tax rate is 35% than 12%. They're also far more likely to be able to plan on setting aside some portion of their incomes into a FSA at enrollment time rather than the bigger effects of the gamble with lower income earners; the outcomes of the risk of overfunding is way more impactful for someone making little money.

The tax benefit helping the wealthy more seems to me to move more towards eliminating the tax advantages of healthcare spending entirely.