The biggest problem with Boost isn't simply the number of headers - it's maintaining the built libraries against your compiler. "Let's upgrade to MSVC 2015!"

The biggest problem with Boost isn't simply the number of headers - it's maintaining the built libraries against your compiler. "Let's upgrade to MSVC 2015!" "Oh nuts, our code now links against msvcrtp13.dll and our built boost_filesystem.dll still links against msvcrtp12.dll. Time to rebuild all of our libraries!" This is especially bad on Windows where MS's dev tools team just didn't 'get' that developers just don't care about new CRT optimizations if it means rebuilding all of our 3rd party libraries. But even on OSX there's been the whole libstdc++/libc++ pain. Anything that can get folded into the standard library and maintained by the same jokers who rev msvcrt*.dll every couple of years (rub their noses in their own mess) is good.