Why did the Driver need his moonlighting job?

So I get that the Driver longs to escape his criminal environment and live a normal life. So why does he moonlight as a getaway driver in the first place? Couldn't he have made a living as a mechanic and stunt driver?

I get that the movie implies that crime or perhaps the thrill of the chase is simply in his nature, just like the scorpion on his jacket whose nature is to be a predator. But this isn't like mafia movies where they never let you leave. All he had to do was stop taking on new jobs.

I also understand that he takes on the ill-fated job with Standard because he wants to help Irene and Benicio, but I'm talking about his motivations before meeting Irene.