IIRC, since GCC got covered by GPL3.
It used to be slower and I've spent way too much time working around C++ bugs in GCC 2.95
(The fact that I remember the problematic version is telling :)
They changed their major release numbers too tbf. 4.x it was point release per year, now it's a major release per year.
Everybody remembers that specific version :). And I wasn't even programming professionally at that time!