The top comment nails the true cause of the problem - “The upper classes are just pitting us against each other. Broke delivery driver and broke customer who ordered the food will fight each other over tips, whilst the food delivery app makes good money and laughs at us fighting.”
Tip culture is just plain broken. It’s a way for capitalists to shift the responsibility of paying for labor to consumers, which also allows them to deflect any blame when it comes to tip amounts.