If service to others and to society mean anything to you, working in Starbucks or any fast food job will teach you more about humanity and human society than most college grads learn from a humanities degree.
Helping a mega-corporation make an extra buck is not "service to society".
If you meant doing a service job at a small business, where you can have real ownership over how it treats its customers, I would agree with you.
But will it help those baristas pay off the student loans that paid for their philosophy degrees?
It’s difficult to articulate the tedium and monotony of a Starbucks gig. There’s so little intellectual stimulation available in that setting. If you managed to learn more from your fast food than your humanities degree, then I think that’s on you for not paying attention at college (perhaps because you were exhausted from your job?).