There are two main reasons that evangelicals oppose government social services. One: Communism bad (well, "socialism bad" now because they have to poison the well against European democracies now that USSR is gone). Two: If the government helps people, people will be less likely to seek help from evangelical organizations, which eliminates a huge way to market Supply Side Jesus to people. Eating in to evangelicals' ability to proselytize compellingly is therefore a non-starter.