https://www.gnu.org/licenses/why-assign.html
Some large companies followed suit. The most interesting is Oracle, which went half way: Their agreement makes Oracle and the developer joint owners of the contribution.
https://www.oracle.com/technical-resources/oracle-contributo...
Rich Hickey later adapted their form for Clojure. I'm sure it's happened elsewhere in the Java community.
Opinions on license-versus-assignment this still differ. But other GPL-o-sphere organizations, like Software Freedom Conservancy, have done more public enforcement of late than FSF, without assignments. Especially for the Linux kernel, which has never consolidated copyright ownership in a single organization.
https://sfconservancy.org/docs/blank_linux-enforcement-agree...
Apache is a bad example. While Apache committers do have to sign a CLA, they don't transfer copyright by doing so. A better example is the FSF whose CLA requires copyright assignment.