"The dabbawalas have deeper reasons for doing it. Serving their customers is like serving their god.”

It could be because they see their purpose as delivering food to people on time and it doesn't seem like the nascent services have figured out how to do that well at scale - thus they may make more over there but are less fulfilled in their life mission?

Swiggy and other delivery startups are more demanding in work hours (to make good money you need to do late nights weekends etc) and also needs you be able to drive a scooter . Also these startups need you to be able use their mobile app, maps and gps and find the customer these require literacy and few other skills Dabbawalas may not have readily.

Dabbawalas are more involved with transporting home cooked food to the worker. The worker leaves early in the morning and some time later the spouse will have a hot meal packed up. The dabbawala will come pick it up and aggregate orders going to common destinations, move it by train, etc. I presume Swiggy is only for restaurant cooked food.

Secondly the dabbawala jobs are more like a stable union job. You don't get the top money but everyone looks after each other. Of course with time customer preferences may change towards restaurant food. Or maybe workers start using plastic containers and microwaves.