You are eligible to deduct your contribution now and you anticipate your tax rate at retirement to be lower than your current tax rate.
You need a tax deduction, lowering your current tax bill. (Some investors still contribute to an IRA account even without the tax deduction).
You are looking for a larger choice of investment options for your funds.
You are not eligible for a Roth IRA.
You are allowed to make contributions even if your income is above the earning limit for the year, however the contributions are not deductible but the earning grow tax deferred.