The reason SFTP is not a part of
SQLBackupAndFTP is because in our estimation we see the effort of adding it to be greater than the reward our users would get. We would add it if we see enough demand, but we don't now.
Obviously FTP is not secure. However if you use AES encryption for the backups - your data is safe even if used through FTP. Same applies to your comment about Dropbox being unsafe.
Also we see more and more of our users to switch from FTP to cloud services for backup storage, so FTP is becoming less important and we concentrate our efforts on cloud.
