To be really honest, neither of these reasons add up. Are you really suggesting that restaurants are losing large chunks of dollars yearly in every order to keep their staff and themselves "passionate"?
Doordashes filings as a public company have stated that the average revenue share with restaurants is 18% and maximum is 30%
That number includes chains. Those restaurants (McD's for example) get preferential treatment - they are on the front-page and they pay no or little commission. That would skew the average. And maximum probably does not include all the potential add-on fees.
Doordashes filings as a public company have stated that the average revenue share with restaurants is 18% and maximum is 30%