Is the pie fixed? Do people have to lose in order for there to be winners?

There is no fixed pie. Everyone is useful because your time is scarce.

Everyone grows the pie and everyone wins. You can only produce so much of something at any given time. People have to take breaks and go home at the end of their shift. While you're on a production hiatus, someone else can produce what you're producing, and profit. More stuff for everyone, which brings more eyes. You won't be able to satisfy everyone. Be it because of proximity, the product is sold out, or too expensive. The benefit of having more people produce the same goods, is that people get their needs met. Regardless if you produce less than the big corporation, you're filling a void that's created by the scarcity of time, while also adding value.