Most companies run a well staffed documentation department. Or, alternatively, employ the services of the owner's daughter because “she always wanted to do something with writing” and “has written a term paper using her MacBook”.
At the very least, they hire an intern during the summer holiday in order to bring the documentation up to date. Starting with the electric can opener that the owner's great-great-uncle had developed in 1927...
As you can see, documentation is by no means an afterthought driven by legislation and dubious directives. It is instead an integral part of product development, customer care, and marketing. As a result, technical writers usually find themselves near the top of the company hierarchy, right between building maintenance and the lady who sells cookies in the cafeteria.