Gig work is great for easily defined, repeatable tasks. Uber is going from point A to point B. This is something done for a long point of human history, and can be easily optimized through maps and routing algorithms. General software development can be more murky, because usually:

1. The person writing the requirements doesn't fully understand what's needed from an eng perspective 2. They need someone to describe tradeoffs of eng approaches 3. They'll probably need custom changes due to shifting business or client needs 4. They might need someone to guide them on a better framework or eng setup for their project

Being able to actually complete a task well, on time or faster will get you a premium (it can be really hard to find). Being able to assist on a consulting side on top of that is very valuable and rare. I think the people who are really good on Upwork often get hired outright by contractors with more money or get higher paying side gigs (or they are outsourcing their work to other devs).