Let's steelman this. Net taxpayers are overwhelmingly childless couples and single men, in that order. To your point, their incentive to preserve a country is weak since they'll be long dead by the time any long term policies come to fruition. Single mothers and couples with children are the greatest tax recipients, in that order. They have an inventive to care about the long term because their children will bear the consequences of their policies. However, they also have a strong incentive to vote for gibs now and screw their future. So which do you want to favor for voting? The ones with no theoretical care for the future, or the ones who theoretically care for the future but are observedly voting to destroy the future?