There's also no radical developments which change or automate prescribed or preventative care, with some illnesses resulting in very expensive hospital stays.
Healthcare salaries are also not expected to drop long-term, and will probably increase.
Cancer rates also go up as you age, resulting in chemotherapy and other expensive forms of healthcare and tests.
Insurance also fights to avoid paying out, and they're probably not keen to stop doing this, either. You generally become more expensive to insure as you age.
Healthcare law is also subject to intense debates within the US, and every change of administration brings risk of those laws changing.
Costs of developing drugs and procedures is also probably not going to go down either, resulting in pharma companies having to charge more per pill to recoup their costs (even if you ignore price gouging from Wall Street investors and free handouts to poor people).
And in the background, you have chronic illness costs (diabetes) and insurance premiums which always add up the longer you live. As well as environmental regulation and disasters which may expose you to harmful stuff.