Why shouldn't everyone be equal? Well...
Imagine you're in a group of 50 people who are living in an island in the middle of nowhere, cut off from civilisation. Together you set up shelter, forage for food, start trying to make clothes out of palm leaves.
All of you are busy all day. Then one day one man says "hey actually, I just want to lie on the beach all day and relax".
You and others say "no, we need to keep working so that we can eat" and you continue working hard all day long. Would you be happy to give the food you've grown to the lazy guy sunbathing on the beach?
I personally wouldn't. I would want to keep my hard earned food to myself and the rest of the group who actually worked for it. If I were forced to give the food to the lazy guy, I might decide to just stop working myself. I'll just join the lazy guy and get free food as well.
If everyone else says "good idea, we also want to laze around on the beach and get free food", will there be any food to eat? No, you'll run out very quickly and everyone will starve.
So then someone has to step in and force you to work. So you're working at gunpoint to produce food that then is given to all the lazy people on the beach. You are angry and resentful. You purposefully do a bad job and produce as little as possible. There is not enough food for everyone because not enough is being grown.
Countries that have tried pure communism have all failed. Millions died in China and the Soviet Union due to starvation. Nowadays there are countries like Cuba and modern-day China that are supposedly socialist/communist but in practice have adopted a lot of capitalist ideas. And even then, just ask yourself - where would you prefer to live and where would you have a better quality of life? The UK or China? I suspect you'd answer the UK.