> Who out there is seriously using a compiler churned out in a weekend?
Someone at a chip manufacturer writing something for a brand new chipset, for example. It takes a long time to get stuff shoved into GCC. It's only in recent history has life settled on one or two "big" compilers. There are still plenty of other places where you will find bespoke compilers. Perhaps not commonly, but they do exist (especially in embedded).
From my experience, while many MCUs have settled for the big compilers (GCC and Clang), DSPs and some FPGAs (not Intel and Xilinx, those have lately settled for Clang and a combination of Clang and GCC respectively) use some pretty bespoke compilers (just running ./<compiler> --version is enough to verify this, if the compiler even offers that option). That's not necessarily bad, since many of them offer some really useful features, but error messages can be really cryptic in some cases. Also some industries require use of verified compilers, like CompCert[1], and in such cases GCC and Clang just don't cut it.
Someone at a chip manufacturer writing something for a brand new chipset, for example. It takes a long time to get stuff shoved into GCC. It's only in recent history has life settled on one or two "big" compilers. There are still plenty of other places where you will find bespoke compilers. Perhaps not commonly, but they do exist (especially in embedded).