Too poor to pay taxes

Conservatives I know keep bitching about how half of Americans don’t pay taxes.* I think their position here is kind of horrible: they see “46% of Americans don’t pay federal income taxes” and demand that they pay “their fair share.”** Isn’t a better question why are half of Americans so poor they can’t pay income taxes?

*This is wrong on its face. Half of Americans don’t pay federal income taxes. When you take into account payroll taxes, state taxes, etc, poor Americans are still paying a big chunk of their income on taxes.
**Which they already do.