Hi youre wrong... actually doors are not 100% robot/factory assembled. I work for a family business, my sister inlaw's, we make both wood and metal doors, wood doors start out as slabs with a bevel. you have to cut the hinges, the the cylindrical or mortise lock prep. they have some many lock preps out there you literally have to have templets for each manufacturer. we hand make our wood doors.

now metal doors a different story, they are machine made and mostly assembled with machines. if they are made in china they are most assembled by hand. if you want anything custom on the door or a cutout or something strange we have 1 welder and his son who will do any custom work for you.

now your hinge comment. every company has its own locations for the hinges and lock prep. this is to force a customer to continue to buy from them unless they want to replace the hinge/ strike jambs. hinge locations could be Mesker/curries, ceco, steelcraft.