The reason why communism does not work is that we are not robots. It is an excellent theory, but it just does not work! Here is why: Pretend that four people decide that collectively they will plant, care for and then equally split the harvest of a garden. On day one, the four people plant the garden. On day 2 Tom pulls garden duty, the next day Mary pulls garden duty, on day 4 Harry is up, and on the 5th day Jane preforms her duties. During the first month the four take turns doing there assigned jobs in the garden. On the firs day of the second month Tom is having a bad day, and it is obvious that his labor suffers because of his day. However Tom breathes easy because he reasons that since the full burden of the garden is not on him all the labor should eventually get done. The week goes by, and the upkeep of the garden does not seem to have suffered much. As many of us have found out by now 'sometimes when it rains...it pours!' And Tom had a tough time catching a break. Week after week Tom was unable to fully devote his mental facilities to the garden, but sense the main crop in the garden was potatoes everything looked alright. At harvest time the group equally divided the harvest, which obviously suffered due to untreated conditions.
The above story is just a brief look at what communism (a socialist form of government looks like) I am not arguing that some people fall onto hard times and they need a helping hand, but I am also not going to look away from the fact that communism can hurt many people (i.e. you will do the same amount of work and receive less when other people pull there load)
One of my favorite book of the Bible is the book of Ecclesiastes. And in chapter 4 verse 4 of that book it explains that capitalism is the way that this world operates. -Then I saw yet another thing: envy fuels achievement. All the work and skills people develop come from their desire to be better than their neighbors. Even this is fleeting, like trying to embrace the wind.-
So if you take away the ability for people to compete, and you make everyone the same then you just put water on the flames of achievement.
Although communism sounds like a very fair system, the only thing that communism accomplishes is to equally distribute misery. It's talked about in the Bible!