I've recently come to the conclusion that making the user's life as easy as possible is a bad thing. It forces extreme design, interface, and development limitations on projects for the sole purpose of making a product idiot proof, often losing the purpose of the product altogether.
Considering that, the case for bundling should be as follows: does it simplify the product to bundle? Not significantly, but does it reduce the number of steps necessary enough to make a noticeable (or perhaps only a subtle) impact? OR, does it combine services together in a way that makes sense, potentially making the process more complicated but conceptually simplifying the user's life/general experience?
One product I worked on was a digital dayplanner for mobile. You can imagine how difficult that is; scheduling, calendaring, task management, contact management, and notes...all in a single mobile app! That was 3 years ago, and today most apps with any of those functions only do the one thing. But there's a strong case to bundle them together: you may want to schedule a calendar event with a number of contacts surrounding a set of tasks and notes. This happens every day.
Our challenge was clear: create a mobile app (since your dayplanner goes with you everywhere) that is easier to use than a paper dayplanner, with all of the expected functionality. Scheduling was excessive; all web-based calendaring tools provide that today, but it was also one of the company's selling points. It failed, and the biggest reason (based on customer feedback, analytics, and our own analysis) was that it was too much. Or, at the very least, we didn't make it useful or beneficial enough for users to continue with the product instead of using an assortment of apps in tandem.
That's why Microsoft, in the last two years, purchased Acompli, Sunrise, and Wunderlist. Acompli (now Outlook) handles email, contacts, and files, and also has calendar support. Sunrise handles calendaring extremely well. And Wunderlist handles task management really well. They all now work with the Office suite, each it's own app. Because as Microsoft is doing it, the focus on major use cases is clear: email often requires calendaring; calendaring is also standalone (though perhaps won't be forever); task management is standalone; and they all revolve around major productivity tools like Word, Excel, and Powerpoint.
So is bundling better than not bundling? Depends on a lot of things, but most importantly...it depends on how you build it, and how deep the functionality is. Further, it depends on the platform; I don't want Slack integrated into an app on my iPhone in a half-assed way when the standalone app is extremely powerful. But who knows, maybe there's a good case for it that people need/want.