I have a business. That business deals in copyleft software that I have sole copyright in (or comes from permissively-licensed code).
My customers, which will be businesses, will be required to sign a contract with a CLA so that if they make changes, I will be the copyright holder of those changes.
No, I won't have individuals sign a CLA. But I also won't accept contributions from individuals, like the SQLite authors, who need a guarantee that all of their code can be public domain.
In this way, I will be legally able to loosen the license over time if I so wish. Without CLA's for customers, I couldn't do that.