You're confusing socialism with communism. Socialism is a political philosophy, whereas communism is one specific (but not the only possible) implementation of that philosophy. Socialism is also intended to be a criticism of and attempt to redress the immorality of capitalism, so morality does enter into it, at least in theory.
Socialism as it's understood now is a specific plan for replacing Capitalism, tied to a specific theory of history, not just a philosophy. At the level of implementation, it isn't morality, it's economics and politics. There might be morality behind it, but there's morality behind all actions, to some extent.
Many modern capitalist governments, including the US, employ socialist programs with no intention of overturning capitalism itself.
And the entire thesis behind socialism is that it's morally superior to capitalism, in a similar way that free software is argued as being morally superior to proprietary software.
