If you've got a lot of experience and connections, finding freelance work on your own is easy. The thing that feeds sites like upwork is people with less of that, people that will work for pennies, often from third world countries. For me, a few years ago I was in school and wanted some income from programming. I managed to get some work on a site that has since been bought by upwork, worked for $10-15 an hour. If not for that site I'd have never gotten that work, and be much worse off now.