Because your earnings can get tax deferred. Also, starting from this year, non-deductable IRA is used as a bridge for Roth IRA - You contribute non-deductable IRA, then convert into Roth IRA ASAP.
Because your earnings can get tax deferred. Also, starting from this year, non-deductable IRA is used as a bridge for Roth IRA - You contribute non-deductable IRA, then convert into Roth IRA ASAP.