For the gig economy, it is not about revolutionary technology, it is more about compound network effect. Basically, is adding (1000*n)-th unit to supply side of a 2 sided market place much more valuable, than adding n-th unit? In case of Uber, Lyft, Airbnb, any delivery service it is true. Having 10 drivers in your area make an app unseable for a rider and they need to seek other way of transportation, but having 1000 can be a game changer, it can make coverage and waiting time so convenient, that riders will always be able to use the app and will never want to seek another option. This, in it's turn, will feed back into the system, as drivers will always have work when they are online. On top of that, the market place takes upon quality assurance. If you did not like the delivery, you leave a negative feedback and move on.
In case of Uber, because of improvements in cars safety, reliability and easy of use, and navigation apps, it made it possible to reach that critical mass/density of supply to have a compound effect.
Apps like Wag will never have this, because dog walking is too personal. It's like cleaning, baby sitting, hair dressing. If you find someone that you like, you tend to stick with them. So if supply in your area growth 100x times, you still gonna use the same provider, because simple 5 start reputation system maybe fine for short stays or rides, but not adequate to match your personal preferences. Grocery shopping, on the other hand, can be commoditized. If you have a list of brands/suppliers you like, you don't care at what grocery store it was bought at and who delivers them to your doorstep.