Federal income tax gets all the attention, but for retirees, state tax can be a bigger ongoing cost. California taxes retirement income at the same rates as wages — up to 13.3% for high earners. New York similar. Many states tax pension income, IRA distributions, and Social Security.
Move from California to Florida and a couple with $200K of retirement income saves roughly $14K-$22K per year in state tax. Over a 25-year retirement, that's $350K-$550K. For some retirees, state tax savings alone justify the move.
But: the wrong way to do it can trigger years of audits and back-tax assessments. The 'sticky' states (CA, NY, NM, SC, VA) are notoriously aggressive about chasing former residents who didn't properly establish exit.