But they are not the only commercial vendor doing this.
Many in the open source community only know GCC and tend to think everyone supports everything.
Since the early K&R C days, each commercial compiler vendor implemented the parts it liked to implement, while leaving out parts they were not so keen to provide.
In the bad-old-days, of course, there was little choice but to use whatever (typically bad) commercial compiler one had available. So although these compilers generally sucked, that was just SNAFU.
But now things are different: GCC, and now Clang, provide high-quality and timely support for a wide variety of targets, and have set the bar much higher. The sucky commercial compilers of the past aren't really acceptable anymore.
Many in the open source community only know GCC and tend to think everyone supports everything.
Since the early K&R C days, each commercial compiler vendor implemented the parts it liked to implement, while leaving out parts they were not so keen to provide.