ERP vendors generally have a whole bunch of standard applications ready. Things like inventory, sending out stuff, payroll (for X number of countries), ...
Long before I ever heard of ERP, I worked on the Burroughs accounting systems. They had inventory management, accounts payable, accounts receivable, payroll, subcontractor accounting etc., all feeding into the general ledger.
So is that really what ERP is? Is it what used to be called an accounting package?
Whether it makes sense nowadays to continue stuffing these all into one system centred around the general ledger is left as an exercise to the reader.
Most of these are built on a gimmick, the same as in the Open Source world. Every database has "their thing". Mysql "is fast and simple". PostgreSQL supports everything you could possibly want.
Oracle has their "fantastic" SQL compatibility and their fast clustering solutions. SAP has their "live indexes". Of course, both have implemented each other's features, and so has PostgreSQL at this point. So that apparently makes them great developers of timesheet software, right? Apparently to MBAs this makes sense.
These companies are essentially consultancy software development companies that have an in-house "core" software (Oracle, SAP, ...) that they can work with really well (in theory), and have standard solutions for many problems on that core. But 3 ABAP developers aren't that different from 3 PHP developers: they all do things slightly differently. And, yes, I do think SAP ABAP is "kind of" PHP. You can even make it look pretty similar, though it uses their internal stuff, not HTML. These companies are selling "quick" and "standard" business software development.
There are major differences too, though. SAP stores all it's code in the database itself, which prevents all development tools, from vim over git to CI/CD from working.
Of course this would mean Wordpress is ERP software ... and it kind of is, with enough plugins.