I'll tell you a little story of why. There was actually a country where its leaders had a beautiful dream in which they would ditch capitalism and everyone in society would share resources and be equal. This grand, amazing and inspiring egalitarian revolution became known as "Year Zero."
What this meant in practice is that many of the businessmen, professionals, intellectuals from the city - highly suspicious folk, as they had much more than others you see, so they had to be dealt with first - were sent to rural fields where they would work the land and contribute through labour to the great project of total equality. Turns out that growing crops that way is highly inefficient so many of them were worked to death, or else starved to death. Anyone that objected was often simply shot on the spot. Because if you are truly serious about everyone being equal, well, sadly you have to eliminate those greedy bastards trying to sabotage the grand utopia. You can't make an omelette without breaking some eggs!
Now here is the interesting part: If any of these starving workers happened to come upon a piece fruit that had fallen on the ground, they were NOT to eat it, under penalty of death. For if they did, they would have more than others. This is the sad sacrifice people had to make so everyone would be equal. In the capital of this country, the leaders of this glorious system were in the meantime stuffing themselves with five course meals of fine cuisine every day. They all got fat from eating so much. When you are leader, the concept of equality becomes a bit more flexible.
The name of this country is Cambodia, and in the 1970s with the goal of ditching capitalism and making everyone equal the Khmer Rouge ended up killing 2.5 million people. There is a place in Cambodia where you can go and they will show a tree - and that's the tree where soldiers would take babies from the arms of screaming mothers and bash their brains in front of them.
Lest you think this was a solitary experiment that simply went wrong, far from it. Forced collectivisation has been attempted repeatedly, from the Soviet Union to Maoist China and elsewhere, and the recurring pattern has been consistent: economic failure, brutal coercion and extreme human suffering. All that varies is the scale of the destitution, brutality and mass death.
Difficult to know what the greater tragedy is: the millions and millions of people already killed in the pursuit of these utopian experiments, or that there are still people that can't be bothered to read a history book (or else studiously ignore their screamingly obvious lessons) and are determined to repeat the awful experiment again and again. Hey, it's only 100 million dead so far, maybe next time we'll get it right!