Ignore the “famous” bit for a moment. They’re all just freelancers to a greater or lesser extent, you’re just more familiar with their work than most. To be fair a day spent doing a car advert is probably quite lucrative compared to 6-month spent making a film and being paid as a percentage of the profit that it may or may not make.
Would Binners have done the same if Just Eat had phones him up asking for a new logo despite his long standing association with Gregs?
As others pointed out, being cool doesn’t keep the lights on, even less so if you were cool 30 years before instagram likes and youtube made it a monetizeable asset!