Why SUBMITTER as parameter and not as seperate command in ESMTP?

Why do you want to add a paramater SUBMITTER to the MAIL FROM command 
instead of adding a new command SUBMITTER to the ESMTP protocol? So we 
can check if a server understands SUBMITTER at the EHLO command.
This is only because some MTAs that are not patched have problems with 
SUBMITTER in the MAIL FROM command.
Regs
Teddy