My reasons are whatever the Catholic Church's reasons are.
The Catechism of the Catholic Church has a little more to say about it[1]:
> (2425) The Church has rejected the totalitarian and atheistic ideologies associated in modem times with "communism" or "socialism." She has likewise refused to accept, in the practice of "capitalism," individualism and the absolute primacy of the law of the marketplace over human labor. Regulating the economy solely by centralized planning perverts the basis of social bonds; regulating it solely by the law of the marketplace fails social justice, for "there are many human needs which cannot be satisfied by the market." Reasonable regulation of the marketplace and economic initiatives, in keeping with a just hierarchy of values and a view to the common good, is to be commended.
My pleasure, I always enjoy sharing what I firmly to be the truth. I guess that's a pretty common attitude here on HN, but I seem to be the only one who believes that truth is found in the Catholic Church.
I'm sure it can be a kind of lonely around here for Catholics. For what it's worth, while I'm no longer conventionally religious, and while even in my religious days the Catholics were considered to barely qualify for heaven (Evangelicals being Evangelicals), I've come to have a somewhat more nuanced perspective on 'you guys'.
And I definitely think having views like yours over here is a benefit to the 'community'.
The Catechism of the Catholic Church has a little more to say about it[1]:
> (2425) The Church has rejected the totalitarian and atheistic ideologies associated in modem times with "communism" or "socialism." She has likewise refused to accept, in the practice of "capitalism," individualism and the absolute primacy of the law of the marketplace over human labor. Regulating the economy solely by centralized planning perverts the basis of social bonds; regulating it solely by the law of the marketplace fails social justice, for "there are many human needs which cannot be satisfied by the market." Reasonable regulation of the marketplace and economic initiatives, in keeping with a just hierarchy of values and a view to the common good, is to be commended.
[1] http://www.vatican.va/archive/ccc_css/archive/catechism/p3s2...
(This book, online free at that link, is an immensely helpful resource on a huge variety of topics.)
And here's the Catholic Encyclopedia's entry on Communism: http://www.newadvent.org/cathen/04179a.htm