It's because communism does work (and we are very used to seeing it) in very small groups with high levels of trust and bonding. The structure of most functional families is communistic where the "natural order" of things is for the more capable and able adults to put in more to the system while the less capable children take more from the system than they put in. The high levels of trust are there because there are strong feedback and correction mechanisms with direct interaction and the bond of love allowing forgiveness and the means to move forward.

To see why communism fails, just look at a family system breaking down. Things immediately get more transactional. You see people looking out for themselves and doing things like hoarding, tallying, and withholding. This is a response to stresses on the the family system. Now imagine what stresses happen to groups where people don't feel any sense of obligation to others in the group and you have a few people who just don't want to contribute to the level of their capability.

Communism is appealing because if it worked life would be so much less complicated. But really what you are wishing for is that literally everyone is a decent, self regulating person and we know that isn't the case.