Why exec subsystem from shell and not directly?

[Asheesh Jadav]

Hi,

  This question is probably not specific to SSH but SSH uses this approach
so I'm posting here. When SSHD receives a request to run a subsystem (say
sftp), why does it FORK and EXEC a Shell with "-c /usr/sbin/sftp-server"
instead of FORKing and EXECing "/usr/sbin/sftp-sever" directly? What value
does execing the shell add? Appeciate any info or pointers.

TIA