The web wasn't really created for the use that is given today and we're using our browsers like a pseudo-OS, this causes that webapps can't talk between each other and it requires a specific integration with each one of the services you want your app to communicate with.

However, when you develop an app for Windows or Mac you needn't worry about integrations, it's already integrated with all the installed programs on the computer out of the box, it's the OS who is in charge of managing the communication between apps.

To me it seems that we don't really use our OS anymore, we do all our work online/cloud (Dropbox, Drive, Slack, Trello, Gmail...) so it makes sense to unify all our services into one place