The advantage SAP has from an enterprise's point of view is "automated" accounting that theoretically can be integrated into third-party software, like the software that sends out bills via mail to customers.
Usually SAP is too bloated for everyone, in Germany we would say "mit Kanonen auf Spatzen schiessen" because it's too much overhead for maintaining/licensing the system vs. just using a simpler alternative that likely even is open source and can be modified quickly to your needs.
From a selling point of view, SAP is always sold as "it can do anything out of the box" without any development resources necessary. While that's far away from the actual truth, most CEOs believe that kind of stuff and just buy the service; which is contracted in a way that it has a minimum lifetime of years (usually 10 years+) until you're allowed to change to an alternative.
Legal requirement to archive all bills 10 years does the rest, et voila, you have a working Dip nobody can exit out of.
Immediately, SAP NetWeaver comes to mind. The whole architecture, concept and experience is violating every possible UX guideline of any operating system - and has never been updated since the 80s.
Every single person I've talked to hates SAP for various reasons. Nobody understands why there's no alternative, and nobody understands why SAP exists in the first place. And everybody hates that SAP created the optimum lock-in scenario; where they fictionally created the maximum amount of cost for companies trying to switch to another, more modern, system.