I don't trust third-party clouds for many reasons; for one, what's to stop them from holding my data hostage and making me pay a ransom? Or just charging for the service with no (or difficult) alternatives? How do I know the data is backed up well, so a server farm fire won't destroy it? How do I know how secure the cloud is, physically, by host, by software or any other way? I'm sure I could easily come up with a half-dozen other reasons why it's a concern without trying very hard.
I find it hard to believe that any cloud service with some basic primitives couldn't host my data just fine. Why must I use everyone's individual cloud service?
This complaint is no doubt semi-bogus in this case since it's OSS software, and I could fork it and add Dropbox support. That's valid. But everyone is using their own cloud, and it's bothersome.