The Next Stage of Ride Sharing

It occurred to me as I was looking at a report on Uber today that the competition on ride sharing means that companies (and the ride sharing companies) are missing a big opportunity.  

I read somewhere that Walmart is using the taxis that sit outside their store to deliver goods to people who order online. We all know what happened with WebVan, but does that mean that the concept is flawed or that it was implemented poorly/prematurely? Google and Amazon are racing to get same day delivery implemented so that they can compete with physical retailers. But even physical retailers require you to come to their stores. 

So, if I'm a small business, why can't I just use Lyft to be my delivery service? Either as an add-on fee, or a contract where drivers in a neighborhood pick up whenever they're in that neighborhood (they can pick up fares along the way) and the drivers get a regular monthly rate based on number of pickups they do that month.   (Or they can utilize the rideauction marketplace to determine best rates.)

It doesn't make sense to pay a taxi fare to deliver a sweater. But why can't the sweater hitch a ride? (I know that it's not quite that simple - there's liability and timing, etc - but if Walmart can make it work in Brazil, it should be workable here.)

Again, since we're headed toward a world in which every consumer is an entrepreneur, why shouldn't businesses be the customers?