Maybe for projects such as OpenSSL and other "infrastructural" software, but choosing a copyleft licence for e.g. a compiler/runtime library would be IMO a mistake. For example, LLVM chose a non-copyleft open-source licence, and one of the main issues preventing OCaml from becoming more mainstream is its horrible licence (which is actually much worse than GPL, as it requires that all modifications to code be distributed as original code + a patch).
GCC is (unsurprisingly) copyleft and incredibly mainstream. QPL patch requirements are a big hassle for distros, although Debian has special casing in dpkg building to handle it.
GCC's traction is mainly due to it being, for a very long time, the most complete and widely-ported open source compiler system available.
Its competitors tended to be expensive commercial options, or comparatively limited open source projects. Any individual or organization wanting to use an advanced, yet free, compiler system generally ended up with GCC by default.
It wasn't GCC's licensing that attracted them. In fact, its licensing ended up being a liability, especially for commercial users. That's why we've seen LLVM and Clang really take off lately. They started to not only match the functionality of GCC, but did so with a far more flexible licensing approach. This made them a much more appealing set of tools for many users, both commercial and open source.
Clang/LLVM are also much easier to work with architecturally, as well as being 20 years newer and offering new ways of using IL; difficult to control for that variable.
