That would be untenable - I wouldn't be able to cleanly `gcc -o blah blah.c` without making an explicit decision, and by extension wouldn't be able to (continue

That would be untenable - I wouldn't be able to cleanly `gcc -o blah blah.c` without making an explicit decision, and by extension wouldn't be able to (continue to) compile existing code either. Rebuilds on every codebase everywhere ever would promptly blow up. IMHO the revolts would come from two camps, a) bureaucracies for whom a build system change would normally take months, and b) individual devs who would be all like "compilation flags?? in MY defaults?! that's LESS likely than you think!". Worst case scenario, someone forks glibc, removes the offending requirement, proffers commercial support for their fork... and ends up making bank.