If I am building a house to sell & you are a plumber who I have hired to do the plumbing in many of the houses I have built, why would you want to be a partner? As a plumber you get paid whatever we agree to as soon as your part of the job is done. You make your money on your labor & by buying plumbing parts cheaper than I can get them thanks to your relationships with plumbing parts producers.

If instead you were a partner in the overall construction of the house then you would have to hand over money in the building process & you don't get paid until the house sells. If there is a downturn in the housing market preventing the house from being purchased you might lose money. Not everyone wants to be a partner.

If I design some new part for a 3d printer & a bunch of 3d printer makers want to include my part in their printers, I just want to sell them my part & get paid immediately. I don't want whether I get paid for work I've already done to depend on other people's sales & business decisions & whether they market their stuff right or run their company well. I don't want to have to argue with "partners" about what is the best course of action. I don't care if my part adds more profit to their 3d printer making business than I collect myself. In fact, I kinda hope it does, that means the income I make is something I am more likely able to rely on.

But I do think it is entirely possible that in the not too distant future, a single person may be able to own the equipment needed to build a house by themselves in just a few days. So basically either way you are wrong.

Again, the problem with the left is that they don't actually know how anything works.