This question already has an answer here:
The F number is a ratio calculated purely from the focal length of the lens and the size of the aperture. Any light meter talks in terms of F, Shutter, and ISO.
Different glass, or just different number of elements, is going to change the number of photons that get though the lens; we compensate for ND filters by adjusting F. What am I missing? Why aren't t stops part of exposure calculations?
In other words, I know what T numbers are, and how they differ from F-stops. What I don't know is why handheld light meters and related tools have no provision to take T into account, but talk only in terms of F.