Why require exchange management tool on the backup exec server?

hello all,

as reuqired by BE Admin manual, we should intall Exchange Managment Tools on the Backup Exec server if you want to backup exchange 2007/2010

but, in my enviroment, I have not install EMS on the Backup exec server, and I can backup my exchange 2010 and restore mails for the users. why?

thanks.