Taxi fees are fixed costs, usually 400-500 baht a day (with free days if you rent for a week), and drivers receive cash payment, no more hidden fees. Grab driver fees are 20% (and more), and 90% of the time the driver purchased the vehicle on credit, which amounts to approximately equal to, or higher, than what taxis pay for their rental, in addition to this Grab drivers can not withdraw 100% from their wallet, there needs to be a floating amount or they won't be able to accept orders.
Grab drivers also need to be aware of taxi mafias in the form of regular yellow plate taxis, and black plates "limos" etc., and if a certain pick-up location has such groups, you surely can understand why they would cancel a ride.
Personally, I would rather walk, ride my bicycle, take a bus, or use BTS/MRT, I prefer to keep my blood pressure within the recommended normal limits.
