I have seen Doordash statements where commission + fees added up to 60% of the price. I asked the person who mostly worked with restaurant owners why they do it. He said:

1. A lot of restaurants are passion businesses and they don't realize how much money they are losing.

2. Morale in the kitchen is important, orders coming in keeps morale up.

From myself I would also add that they get a FOMO, cause it's hard to sit and watch others get business, however unprofitable. The most stable and profitable businesses in towns where we operated only worked with us, cause we offered cooperative ownership and small commission. It made no financial sense for them to work with anybody else.