They do, however, very often use existing language, and custom language is minimized.
> Another type of custom and complex contract is employment.
Where contracts are often almost entirely standard per-company, and often standard between companies. And very rarely is the company in danger from the non-boilerplate clauses.
If you want an example of such a clause, consider Google's own IP clause in its contracts, which contend that Google owns basically all of your IP while you work at Google, unless you take steps to declare ownership of it in advance (and Google approves).
Will this clause entirely hold up in court? Probably not. Do you want to be the one to test it with your multi-billion dollar startup on the line?
The risk of using AGPL software is significantly higher than not, and the benefits are relatively small.