Why aren't C++14 standard-defined literals in the global namespace by default?

Question

C++14 includes standard-defined literals for, amongst other things, std::string and various timespans from the header.

To us

Answer 1

There already are two UDLs named s: one for strings and one for seconds. Due to the understandably terse names of suffixes, they chronically suffer from name conflicts, so pouring all of them into one namespace cannot go well for long. Hence it was decided that they be put into inline namespaces, which allow for both unambiguous (using namespace std::literals::chrono_literals) and simple using directives (using namespace std).