In my area, pizza delivery drivers (read: not DoorDashers, etc. I am not sure what they make since I refuse to use those services) make about $12 - $15/hour and get paid for mileage (usually between $0.50 - $0.62 per mile.) I'm not seeing a reason to tip them. They are making well above minimum wage in my State, unlike the restaurant servers/bartenders that only just barely crested $4/hour as of 2025. The latter is in a position to rely on tips, the former is far from it.
I ask because we don't seem to have an established "hard line" on when tipping is appropriate in the United States, and when it is not. This extremely fuzzy understanding is allowing companies like DoorDash, coffee shops, etc to under pay their staff by off-loading part of the cost to the customer, which makes your $7 latte cost $10, or whatever. It's steamy bullshit and needs to be shoveled into the bin.
If we had a hard line on when tipping is justified, we'd quickly see a change in the other direction. I've always felt that the hard line should be "if you are making less than minimum wage, then tipping is justified." That's it. No soft maybes, no washy-washy justifications.
That being the case, if a barista (avg $15/hour in the US) is not happy _without_ the tips, then they have two options: demand more from their employer, or find a different job that pays better. Either way, the employer is left to consider either raising wages to keep people satisfied, or doing the same just to keep people in the door and stay in business. The barista is, in essence, the face of the company. They do the work the customer sees, which makes them important to the sustainability of the company. Ergo, the company needs to put more resources in the barista's pocket to ensure quality work.
It sort of blows my mind why everyone else in the US does not think this way, but I have tried to dissect my own stance on tipping (from the standpoint of having spent nearly a decade working front-of-the-house in restaurants), and I'm really having trouble poking holes in my own logic. So, I'm always interested to hear other people's takes on why they tip the way they do.