Google has one of the largest software engineering populations of any company in the world. It supports one of the largest developer ecosystems in the world. Games are the largest catagory in their ecosystem. 2 engineers supporting the NDK...
It wasn't there until 2.2, only got added due to community pressure and they always did the minimum amount of work.
When the migration to Android Studio was announced, we got left with no migration plan.
Only after JET Brains announced CLion, almost 2 years later, did they announce the migration to Studio.
Likewise they moved into Gradle without plan for C NDK support and it took three generations of build tools until they decided to settle on CMake.
As an earlier commenter mentioned, games are one of the biggest app categories and many games rely on the NDK. Pro audio could be another big category, but I think Apple has the market sewn up there because Android is still way behind.
(I'm not saying that there's anything inherently unreasonable about that, although I happen to disagree with the decision. But these things cost money and they decided they didn't want to spend the money.)
Most likely due to game development community.
Specially when compared with the tooling support C and C++ enjoy on iDevices and UWP.
NDK team doesn't look like it's expansive or prioritized at all, so I doubt they have resources or will to do that. TBH I'd rather they focus at improving the tooling and debugging, we can ship our own libraries with our own options compiled in. Heck even on iOS we have to ship a custom SQLite to get all the needed capability.