So? NT predates UTF-8. UTF-8 and UTF-16 are both awesome - they provide unicode support.
Windows first shipped with UCS-2 at a time when the rest of the world was stuck with ASCII and various random codepages, then switched over to UTF-16 at around the same time UTF-8 was picking up speed; UTF-16 had the unique advantage of being (mostly) backwards-compatible with UCS-2, whereas UTF-8 would have broken everything. I prefer UTF-8 myself, but that doesn't make UTF-16 a bad choice.
In fact, while for the default ASCII range of characters UTF-16 consumes one extra byte over UTF-8's single-byte encoding, once you get into the "normally-used range" of international characters, UTF-8 quickly jumps to 3 bytes while UTF-16 remains at two.
Windows first shipped with UCS-2 at a time when the rest of the world was stuck with ASCII and various random codepages, then switched over to UTF-16 at around the same time UTF-8 was picking up speed; UTF-16 had the unique advantage of being (mostly) backwards-compatible with UCS-2, whereas UTF-8 would have broken everything. I prefer UTF-8 myself, but that doesn't make UTF-16 a bad choice.
In fact, while for the default ASCII range of characters UTF-16 consumes one extra byte over UTF-8's single-byte encoding, once you get into the "normally-used range" of international characters, UTF-8 quickly jumps to 3 bytes while UTF-16 remains at two.