How many times do you get approached by customers or other vendors about "when are you going to integrate with XYZ" product? If you just integrate ONE time with Zapier, you're immediately connected with over 200 other online services. Then your answer to those customers/vendors can be: "We're integrated with Zapier, so you guys should integrate with them too and you'll get all the other benefits as well". With that answer you accomplish 2 things: 1) you shift the burden to them (2) you can use Zapier as a "testing ground" to see how popular an integration with a particular service is. If one particular Zapier connection starts taking off, then you can consider a direct integration. If only a few people use a particular service connection, then you haven't lost anything.