This profit comes directly from the workers, there is no other place it could come from. Profit is not magically created, it is taken. For every person that gets resources without working, another works without getting the resources they are due.
Without working, yes, but maybe not without having worked? If I have spent the last 10 years of my life thinking up some process whereby I create a product, is it so unfair then if I put the workers to the job of making it? So let's say I create the iPhone. Tough work. Took me 10 years. I can't possibly mass-produce it enough by myself to repay all my labor. So I hire workers. Yes, I get most of the profit from their work, but they didn't labor 10 years to create the iPhone.
I can understand there can be counter-arguments to that though. Like, in real life, the people with the ideas aren't the ones getting the profit or owning the factories most of the time. The people with the great ideas are usually workers just like everyone else.
#1 just because you do something does not entitle you to the work of others.
#2 It is hard to measure the objective value of services but great inventors under socialism often get a lot of resources given to them.
#3 "most of the time." Not just most, I would say over 99.99% of the time, in fact they often do better under socialism