Pre-tax IRA contributions defer taxable income. They do not necessarily lower taxes.
You shouldn't just be looking at immediate tax savings when what you are doing is pushing the tax liability into the future. If you are in a low tax bracket, a Roth IRA contribution likely makes more sense than a traditional IRA contribution where deferring the income doesn't really buy you any tax savings in the long run. Better to get the opportunity for tax-free growth instead of taxable growth. Even a capital investment outside of an IRA would likely be better (although perhaps not better that a Roth IRA contribution) because if you are in a low tax bracket your long-term capital gains could be taxable at 0% (or 15% if you are in a slight higher tax bracket) instead of as ordinary income when distributed from a traditional IRA. Capital investments outside of an IRA also get a step-up in basis when inherited by your beneficiary(s).
The same reasoning goes for a traditional 401(k) contribution. Like a traditional IRA, it defers taxable income to the future, it doesn't eliminate taxable income.
