Any position can be determined from x,y,z, you could just tack on the z coordinate - though you'd need to match that locally, accounting for sea level. If you are using latitude and longitude you should stick with the paradigm for height, since floors can be different heights.
No question, I considered that too. But for determining position in 3d space I think its more consistent than having floors. If you get to say the 10th floor with different floor heights the difference could be considerable. Its the problem with whats practicable in daily use and what makes sense from a system perspective.
