Simply because good encryption tends to be slow, making the app unproductive imo.
gocryptfs is very fast for me. i have a file with about 5600 lines and i detect no difference when opening it under encryption and not under encryption. but in gocryptfs each file is encrypted separately . so you could get some information about the directory structure. but the name of the files and folders is encrypted ("archive" for example turns into something like "AaL6P86WWMnqQkMYnsRBXg").