Quite the opposite; jemalloc has been the default, and using the system allocator has been the "hassle" since well before 1.0.
However a few key platforms have jemalloc disabled because it's buggy (deadlocks or worse). I think as of a few days ago it's pretty much universally off on windows.
Also whether jemalloc is used depends on how you build your thing -- dylibs use the system allocator (because they're subordinate), static libs (rlibs) inherit from the thing they're linked into, and executables use jemalloc (because they're in control).
