This is assuming that I will live for another 30 years (57 now). Even though I will pay income taxes on the money now for 2019 ($1,518), I can still invest this money and only have to pay 15% long term capital gains when I sell. So tying up $6,900 every year to save $1,518 in taxes each year, and only having access to this money only for medical expenses, just doesn't seem worth it to me. If in the future when I have medical expenses that deplete the HSA, I can just make another deposit of the maximum to reduce the taxes for that year, then reimburse myself.
Also, the firm that does my company's HSA does not have a provision for rolling the HSA to a different brokerage firm. It is stated that we have to use their firm for investments, which have higher fees and higher transactions costs, and limited fund choices. The only way I can roll it out of their HSA is if I leave the company. When I start adding up all the costs, fees, and expenses, with very limited fund choices and no options to buy stocks, it doesn't seem worth it to me to have more in the account than what I need to cover my deductible.