If it were not deductible for anybody, fewer people would have health insurance. If you're in that pool, it's good for you, because it would probably be cheaper. But fewer people would be insured, so it's overall bad, right?
Am I'm missing some part of your argument?
The idea of making it universally deductible/subsidized for individuals seems to be the path that we're on right now.
Case 1: If you purchase health insurance on the exchange, and are very poor, you can get fully-subsidized plans. (Not to mention if you qualify for medicare).
Case 2: The most plausible proposals of "Medicare for All" are basically expanding the pool of people who qualify for zero-premium medicare advantage plans. This keeps insurance individualized and operated by private companies to maintain quality improvements driven by capitalistic-competition, although the government is the ultimate payer.
Case 3: the government (yes, even the current administration) has taken several steps to encourage employers to subsidize the costs of employees purchasing insurance individually, rather than as a group [see https://www.takecommandhealth.com/ichra-guide].
I’m for it being universally not deductible. Or at least not deductible for corporations.
The idea is that it forces everyone onto a common public individual market as there would be no tax or cost advantage of corporations to self-insure or provide insurance.
Longer term this gives better mobility to workers and lowers costs of the individual market by bringing in 100M+ healthy people (which lowers the average risk weight cost of insurance).