David,
Surely that is not the only consideration. Another might be that you know the detail is there!
On your reasoning, why also would anyone bother to fit inside working valve gear to a steam loco? or build fully detailed coach or wagon underframes with rivet detail you can hardly see, as opposed to a simplified moulded representation of the same? Its a matter of personal preference, surely.
Regards,
David Parkins,
Modern Motive Power