Because you asked it in a away that implies I said it prevents everything bad and not some bad things. It helps prevent the kind of mass murder and oppression that always happens under socialist regimes.
As opposed to socialism which has resulted is mass murder, genocide, starvation, and oppression in every place it has been tried while do nothing to improve the live of the people in it except for the very few people at the top.
Name me a prosperous socialist country, I will wait.
And of course we just have to assume that even if there was a successful socialist country that it would not have those same problems you blame on capitalism.
When has socialism ever been democratic?