They came with schematics because all expensive electronic equipment back then did. This was back in an era when electronics broke down frequently. Schematics w

They came with schematics because all expensive electronic equipment back then did. This was back in an era when electronics broke down frequently. Schematics were needed to fix things when they broke. If the owner didn't fix it, then an electronics repairman did. You don't get schematics with anything today because you throw it out if it breaks rather than pay someone $100/hr (what auto mechanics charge) to fix it for you. Intellectual property is also a bigger concern today that it was back then. By not giving you the schematics, they force you to do the tedious (but easy) task of reverse engineering their product.