I would suppose that the reason there are 30-day CDs is so you can have very liquid assets. If you have cash that you don't know what to do with, buying a CD is always a plus, so that you can at least receive marginal interest.
Be warned, however. The shorter the CD, the lower the interest rate, so in a 30-day CD, the interest rate will be VERY low (a few points at best I would guess ... but still better than nothing).
So, the real answer to your question, in my opinion is so that you can have liquid assets and still receive some interest. Can it help your credit? Sure, but not a whole lot. It certainly couldn't hurt.
Be warned, however. The shorter the CD, the lower the interest rate, so in a 30-day CD, the interest rate will be VERY low (a few points at best I would guess ... but still better than nothing).
So, the real answer to your question, in my opinion is so that you can have liquid assets and still receive some interest. Can it help your credit? Sure, but not a whole lot. It certainly couldn't hurt.
