My daughter works at Starbucks. There is a shocking (to me) contingent of people who do indeed order $4-7 coffee-based drinks daily. She sees the same people every day. It's mind-bending to me, but clearly normal for many.
It's also a chance to socialize, with no expectations, with other regulars.
It's a treat.
If you're making $100/ week, $30 on coffee is a lot of money. If you're making $2k/ week, it's not moving the needle in a meaningful way.
But me, I might spend close to that amount on graphic novels, or on graphic novels and paperback books combined. I make larger purchases less often, and many people might consider my expenditures wasteful as well.
I suspect many people spending $6/day on coffee have never counted the cost, and might be surprised to realize that they're spending $120/month on coffee. But you've done the math and find it worthwhile, so good for you!