The simple answer is that it usually has to do with the laws of those states. If the sponsor is a liquor company or the prize includes alcohol, certain states can't play. Tobacco companies and prizes are disallowed is other states. I don't know the specifics, but sweeps rules appear to be more rigid in FL and RI. Sometimes a business is targeting a certain market and only opens a sweep to that area. The geographics of AK and HI would make some prizes prohibitive to deliver, so those states get excluded. It's a combination of the sponsor, the state's laws, and the prize itself.