If you are a company that only uses SaaS applications it is an essential discipline that will allow you to run a successful and secure company, as SaaS Management is the only discipline specifically focused on SaaS.  For those companies that use SaaS but only in part the presence of an existing ITAM or SAM system is an excellent base to begin to achieve some SaaS use and visibility. So, SaaS Management is a compliment to your current procedures.