Coincidentally companies stopped including schematics once China started copying everything, so no schematics at least delayed appearance of clones by some time.
China started copying everything or China started making everything?
When it gets to the point where the 10 different companies go to the same white label manufacturer in China and get the same product only with 10 different names on it, withholding schematics as a way to prevent the product being copied makes no difference. It does make things harder for their customers though.