Because socialism appeals to the base instincts of anyone. Socialism = laziness, and most people at the end of the day are lazy.
If someone offers you money for free, are you likely to turn it down, even if it means the breakdown of your society? Probably not.
Look at today. People want to socialize health care even though it will kill jobs, blow up the deficit, and cause rationing and death panels.
People are lazy. That's why socialism gets footholds.