Delivery is a big deal and there are so many players charging fees on top of fees everywhere you look that it seems like this would be an obvious one. We have lots of Clients inquiring about it all the time, but it's complex and tricky to say the least. On top of that the big delivery companies don't make it easy to integrate with them, especially if you aren't some billion dollar company that can offer them access to tons of potential business-customers.
DoorDash is super private about it's Partner features and APIs and Postmates "had" a public API that was very good, but there is no telling if any of that is going to change now that they were bought. The hard truth is, we could make an awesome integration and something could change in 6 months - that's why it makes so much sense to work together, so we can all stay ahead of the curve.
We can integrate Delivery for UberEats, DoorDash, Postmates, etc. into a stand-alone website, a stand-alone script that'll work with any platform you use (and simply connect to your Square Account in the background), a mobile app or even Wordpress or WooCommerce.
Aside from APIs, one of the most popular things that's being done right now is creating "parser" based scripts that allow you to essentially create your own API. We have tons of experience creating parsers and we know what all the 3rd parties are doing, so there's no need to pay them for access to their parser, which usually they charge for by the order - which can add up to be a TON of money - when we can just create it ourselves and make it free for all our Wish List Members.