Maybe so ... but if something as removed from human existence as mortgage interest can be deducted from our income taxes, then surely medical costs can be deducted as well.
But they both distort the market. Health insurance especially. They add not only a “fourth party” for insurance payments, but a third party on incidental and routine healthcare incentives. By encouraging people to fit every last healthcare expense under the tax exemption, they take a lot of price discovery and market incentives from the smallest of health expenditures. In sum, they jack up costs and remove cost-containing free market price mechanisms.
Mortgage deductions are a bad idea, too—but not as destructive.