The idea is that the farmer picks his carrots, puts them in a box and sends them off to the carrot juice guy. When he does this he puts a upc code on the side of the carrot box and then puts the code into the blockchain as I shipped this thing to the carrot juice guy. Carrot juice guy receives carrot juice, makes carrot juice with carrots in box and then says, I used these carrots to make this juice in these 300 bottles. <Blockchain> Ships it to distributor. Distributor says I received these carrot juice shipments. <Blockchain> I then sold 1-30 to convenience store A <Blockchain>. End consumer bought one at 3:30pm and got sick. You have the record of how it got there and how much time it spent everywhere, etc. The thing here is there is no centralized supply chain company who controls everything, everyone just puts it on the blockchain that NO ONE OWNS. This is a net gain for everybody in the network, but there is no centralized profit there, except for maybe some systems integrators working at the edges.
This is why blockchain will probably be this kind of subtle thing that doesn't make anybody a lot of money, but just seeps into industry over time. It's a bit like containerization in a way. Huge global impact, but not really any one company who made their fortune on the container technology itself, but all the companies around it benefited.