Since the IRS will determine your tax rate by how much you give over to your HSA and retirement accounts, they put limits on what you could be saving.
Why?
People with higher incomes pay a higher tax rate, and they often look for ways to build wealth while cutting down their tax bills. Also, the federal government wants to encourage people to save for health care and retirement, so they offer benefits and credits for saving.
However, since there's a bit of a catch 22 as to how you need to have money to save it, the limits allow the government to keep people from evading taxes entirely. As your HSA account can become a retirement account after a few years, the government tries to manage the needs of the many versus the greed of a few.
2019 Contribution Limits
As of 2019, the limit on contributing to your HSA is $3,500 per individual.
If you're over 55, that number goes up to $4,500. As you turn 60, your HSA begins to function a lot like a traditional IRA.
To open up an HSA, you must first have a high deductible health plan (HDHP).