Uh, this is the Microsoft who integrated Dropbox into Office 365 as a first-class citizen, alongside OneDrive.
They've discovered that one of the ways to success, aside from vendor lock-in, is to make your product integrate with as many other products as possible
How would that possibly work? Removing Google Calendar support wouldn't drive anyone toward Microsoft. It would just drive them away from Sunrise. People don't choose their Calendar provider based on Sunrise support. They choose their Calendar provider first and might use Sunrise if it supports their Calendar and they like it.
Hey, since I've got you on the line, so to speak, is there a fix for Exchange accounts on Lollipop coming? I love Sunrise but can't sync my work calendar to it on Android Lollipop, which unfortunately makes it not useful now.
Reviews in the Play store indicate that I'm not the only one hitting this issue, but I couldn't find anything acknowledging the issue on the Sunrise support site.
Pretty sure I'm actually hosted on O365, but I don't think it's relevant. Sunrise doesn't even see the account when I try to add an Exchange calendar. It pops up a message saying something like "There is no Exchange accounts [sic] on this phone". This seems potentially related to the fact that the Gmail app is now handling Exchange accounts instead of the default Mail app.
Here are a couple of reviews that mention this issue:
They've discovered that one of the ways to success, aside from vendor lock-in, is to make your product integrate with as many other products as possible