yes all of these payroll type deductions are highly regressive. Some deduct health care cause they have a big employer (and FSA, HSAs etc) and others get taxed on the money they make, period.
There is no rational basis for any of this health care stuff to be deductible, again, it is asking those who do not get such benefits to subsidize those who do.
The uninsured subsidize the insured, renters subsidize homebuyers, non-parents subsidize parents, workers subsidize owners/investors.
Messed up. Regressive.