You would have to get the design engineers, manufacturing engineers, tooling engineers, accountants, and managers all in a room and have them explain why the decisions were made. I can tell you that I have worn a few of those hats for both OEM and Tier 1 suppliers, and quite often the decisions are made as a result of immediate circumstances, even if it is known that they will look foolish in the future.
The other aspect that you have to remember is the OEM is concerned about initial assembly, and initial assembly only. They care very little about compatibility, ease of service, disassembly, etc. If they can save a few pennies and increase efficiency on the assembly end, they will make those changes quickly.