Not sure if we should blame the engineers. A lot of those mongrel combinations are Asian, mostly Chinese in my collection. I think they feed their screw machines with metric hex stock, so the bolt heads are never 5/8", for example, but 19 mm would be just fine with a 3/4" socket. Worse yet, years ago, was working with British Whitworth. Hardly anything was a standard measurement. Old timers that dealt with MG TC's and TD's will remember the frustrations.
Joe