The difference is in one you're paying a bundle/package price for a whole bunch of services, and in the other you're paying a surcharge for an optional extra. Just as you pay a surcharge to Qantas, or a hotel, or petrol station for paying with a credit card.
Whereas in the first you're paying for a package, just as with airbnb, or even a travel agent for a travel booking with transfers, and hotels, and tours and flights, or even a hotel booking through anyone but the hotel e.g. booking.com, or a TA. Commission is rolled up into all those models, the same as uber.
Cash might be legal tender, but nothing compels anyone to accept it. No laws in Australia require you to accept cash.Never found a taxi or uber that refuses cash.
You can pay with cash...it is legal tender.
Some companies try to make it difficult but I find leaving the item on the counter and walking out works every time....
Can one still pay a taxi with cash these days?
OK - so its not a "package" or "bundle" but the costs are still there and you are still paying for it somewhere.