I suppose the thinking is that by having each employee of a big organization do a small amount of work, they can avoid hiring a central person who just accepts receipts in envelopes and deals with them.
Or maybe that by putting up roadblocks like Concur, some employee expenses will not need to be reimbursed.
The problem is that this requires educating every employee on how to use these systems. That's a waste of time and a drag on productivity. Better to hire that central person who will learn all the quirks of whatever system is used and let the other 99% of the organization do their jobs.
When companies need photos of their employees they find a photographer who provides that service. They don't ask each employee to learn about lighting technique and do the post processing according to a written set of standards in hopes the photos will look consistent. But with Concur that's what happens.