The last-straw motivating reason I switched to nextcloud was because dropbox decided they wouldn't let me sync my files to an ecryptfs file system. (I believe they recanted on this policy a few months later.) I didn't like being held hostage to their bad design decisions, so I left and found a solution that worked better for me. Dropbox has also had some serious security vulnerabilities [1], which left me feeling less than confident in their ability to manage my personal data.

[1] https://nakedsecurity.sophos.com/2011/06/21/dropbox-lets-any...