Traditional jobs guarantee a wage for those 8 hours. Most on-demand services guarantee nothing. I'm glad DoorDash at least guarantees an hourly wage in some markets.
My brother-in-law quit a traditional job to drive for Uber, so he must think it's better. (also, he told me that for the first time, he's excited to work in the morning) It's a pretty competitive market -- if a service doesn't provide enough work, they won't be able to retain drivers (plus many people drive for multiple services, especially Uber/Lyft drivers).
This is a case where money and happiness aren't really correlated. Remember, people get addicted to variable reward schedules, and get bored of fixed reward schedules. Want someone to be more excited to go to work? Flip a coin to determine whether they get paid each day!