That's because a true theory of gravity is still missing. On one hand, we have an approximate high-scale view due to relativity, on the other hand quantum theor

That's because a true theory of gravity is still missing. On one hand, we have an approximate high-scale view due to relativity, on the other hand quantum theory says there should be some particles called gravitons that are the carriers of this force. Both these views should become approximations of the real theory of gravity, if and when it's created.