Holders of health savings accounts are not justunderutilizing HSAs by not saving enough in them, they’re alsonot capitalizing on what could be their greatest feature:investing.

So says a report from the Employee Benefit ResearchInstitute, which reviews the trends in HSA usage from 2011–2016.Its database of 5.5 million accounts, with total assets of $11.4billion as of Dec. 31, 2016, reveals that the average accountholder apparently uses his HSA more as a specialized checkingaccount, instead of as an investment account.

The full report, which looks at account balances, individual andemployer contributions, distributions, invested assets andaccount-owner demographics for the period, finds that although HSAs“offer a valuable tax incentive to set aside money on a tax-favoredbasis for current or future medical expenses,” the majority ofaccount holders are only using them for basic current expenses,such as deductibles, coinsurance and copayments.

They aren’t going any deeper to take full advantage of the taxpreference by contributing the maximum.

But they are using those accounts, since overall, 63 percent ofaccount holders withdrew funds. The average annual amountdistributed was $1,771 in 2016, implying an average rollover of$1,151.

Average total contributions—both individual and employercontributions combined—rose from $2,348 to $2,922 between 2011 and2016. This average was just above the minimum allowable deductibleamount for family coverage, but less than half the allowablecontribution maximum for family coverage.

It also appears that the longer someone has an HSA, the betterhis prospects for financial security. Since the rollover featureenables account holders to build up a balance to tackle unexpectedmajor medical expenses, whether now or during retirement, somepeople are clued in and are putting in enough to grow the balanceinstead of depleting it each year for current expenses.

That’s indicated by average end-of-year balances, by the yearthe account was opened, growing, thus showing that financialsecurity increases over time. Accounts opened in 2004, or earlier,had an average account balance at the end of the year of $14,873,while accounts opened in 2016 had an average $1,027 year-endaccount balance.

In addition, annual 2016 contributions are higher the longer anaccount owner had an account. Individual contributions averaged$3,658 among those who opened their account in 2005—nearly threetimes higher than those who opened an account in 2016, at anaverage of just $1,290.

The report also points out that it’s possible at least some ofthe low utilization of the investment feature could be due topeople with relatively new accounts and not enough time tocontribute the required minimum to invest.

In 2016, 11 percent of accounts opened in 2005 had investmentsother than cash, while just 1 percent among those opened in 2016had actual investments. And overall in 2016, just 4 percent hadinvestments other than cash.

Related: Take our quickie HSA quiz and see what youknow about employer HSA rules