That works until a certain point when the problem keeps growing and individual charity is not enough. That's when we tell the government to step in and/or push for systemic changes or a new system to deal with the problem. Charity helps, but go search how little charity covers compared to real collective power the government is capable of. Some people are greedier than others, many people are losers and get left behind in a capitalist system. We collectivise to mitigate these problems because we all benefit from less homelessness, less hunger, less poverty, less health problems, etc. You don't see any merit in the idea that what is good for your state, your community is also good for you?