I think the model itself is valid, it just doesn't work for certain markets right now.

Companies like Amazon and Uber expand their market through convenience and ease-of-use. I make more impulse buys on Amazon with Prime 2-day shipping and take more taxi rides with the convenience of the Uber app.

The problem is it's hard to extract a lot of value without volume and efficiency/integration. Amazon ekes out as much efficiency as possible, being a large online retailer, and Uber was able to 'disrupt' the taxi industry.

It turns out delivery is expensive and even with good process, you can only get so far with a luxury service.

I suspect the on-demand service will slowly die out until it's revived by more efficient transportation (autonomous cars, drone last mile delivery).