I suspect the fitting of a parking brake or a means of preventing the vehicle from rolling when stopped is a more down to construction and use regulations, than the desire of a manufacturer to have complicated things like hand brakes.Belt and braces approach for me. If the handbrake is fitted, why not use it.
Would you beleive anything any of them state after the emissions scandals. Plus you only have to look at the vast number of recalls issued to know that their best laid plans and designs dont always work as they should.