Things like uptime, support-contracts, having someone on-site within three hours when your multi-millon-dollar-order-processing-SAP-cluster goes down etc are what matter to their customers more than usability (traditionally).
Things are changing and a lot of effort has been put into getting better at UI/UX though. But I haven't been involved with them for several years now so I don't know where they are at or what their current offerings are (I keep tabs a bit on HANA developments but that's it really).
Maybe SAP uses their own software internally and they've all become power users that aren't bothered by the issues that you're having. Perhaps if they used competing products they'd have a better understanding of where theirs is lacking.
SAP still needs to get better at their dogfooding game in some areas (e.g. using our own ticket system products instead of internally-grown idiosyncrasies), but we're getting there.
This is called “dogfooding” and all companies should do it. How can you sell to customers or understand customers if you’re not using the product yourself?
One day I’d love to visit SAP and see how they do their own vacations and expenses. It can’t be with their own software.