Veracrypt question

About cloud storage services: Do you trust these brand softwares, or do you log in into the websites and drag and drop the files in there? I’ve just seen all these fancy software apps that each company tends to release, and im not sure if there’s a point. As long as your files are encrypted, + you enable encryption on your cloud storage service, I do not see the role of these programs, specially if closed source which obviously I wouldn’t run and I assume they are all open source.