While overall consumption remains the same (or similar, people need to eat) there's different supply chains involved in commercial and consumer consumption.

Say you've got a bottling plant that sells exclusively to commercial suppliers. The cost to retool to produce consumer packaged products is non-zero. Your shipping is all geared to commercial suppliers as well.

If you decide to reorient to produce consumer packaged goods this takes some amount of time. The farmers that supply you have a batch of milk right now they're storing and a batch coming up next week. If you can't take delivery, you don't have infinite cold storage for milk after all, they need to dump their milk because they've for another batch on the way they'll need to store. You may also have milk stored in your refrigerated tanks waiting for you to be able to reorient for consumer packaging. If your tanks are full you're not going to get new supplies.

There's a lot of supply chains that have a lot of momentum and they've been optimized for throughput because that's what gives everyone involved the best margins. When demand drops it takes time and money to slow down or adjust the supply chain because of the momentum. Things like milk can be more difficult because they need not just storage but refrigerated storage and shipping.

You might have milk and I might want milk but we're far apart and if you can't get it to me (safely) I'm not going to buy it. That's not to say it's good farmers are dumping otherwise good food. Dealing with perishable things is not the same as dry goods. You can't just add more trucks or warehouses and problem solved.