In any case, perhaps a faulty analogy. But your claim "[...] when Uber undercuts competitors by a large margin using inhumane practices, the competitors tend to vanish over time. In the end, guess who is your only choice." doesn't hold up at all.
I'll put it the other way around if Uber does not attract enough bikers who is going to deliver their food ? It is basic supply and demand. Is there is a market but no suppliers, prices go up. If there is plenty of suppliers (bikers), prices go down. If the middleman (uber) is too greedy and screws the buyer or the supplier they are going to go with another middleman.