Companies develop very unique ways to do their accounting so one barrier is companies have to change their accounting practices to fit into the editorial provided by the software company. Software companies in this space develop elaborate customization features based on what they see in their markets.
Because SAP and the US LOBs developed in differing markets they will have different editorials on accounting baked into their software. The number of customers where the fit is great out of the box will be a subset.
Over the long term SAPs implementations will evolve to be more customizable to reach the same customers. No one in this world is positioned to steal their lunch and this suite with criss LOB integrations will quietly run everywhere, in every major company and every government on the planet. Just give it a couple decades.