Yes because privacy MATTERS, and principles to only use open source and contribute back, even if its "only" a bug report matter too. Encrypting single files and also their names is a pain in the ass even for technical people. Its too many steps and just does not flow. If you have some kind on encrypted container you have one big file that you need to re-upload over and over again to share what is in it. A solution that is encrypted by design and the server never ever knows what is in the file it transfers to different devices is the way to go here and Dropbox and all the shitty for profit services to not offer that AFAIK.