I don't understand why it's a commission price structure. Take uber eats. You buy some price of food, then there's an uber eats service fee on top of that, and

I don't understand why it's a commission price structure. Take uber eats. You buy some price of food, then there's an uber eats service fee on top of that, and then a delivery fee (and you're supposed to tip the driver in addition to the service fee and delivery fee?). It seems like that price structure already clearly splits the restaurant's and uber's (and the driver's) portions, but I guess uber takes a commission in addition to that? Like, why fees and commissions instead of just fees? Consumers would understand that delivery is an added cost, so you just add the cost.