Jeena is right. If you do not take every job they offer you you can be blocked from receiving that money in part or fully. Then you have no money or not enough to get by.
Stating that people only live on the street (and freeze to death during winter) because they won't claim their welfare money is a gross simplification. Did you talk to all/any of them?
[1] There are quite some people living on the street though - especially in larger cities - who for various reasons can't or won't claim their social welfare money.