Why are solubilities so vague? (modafinil solubility)

[m060mm]

I checked every chem database, Merck, etc.

Modafinil is a white to off-white, crystalline powder that is practically insoluble in water and cyclohexane. It is sparingly to slightly soluble in methanol and acetone.

That's the most detailed information you'll find.

'Sparing to slightly soluble' implies a requirement of 30 to 1000 times the molecule's weight in solvent to create a solution.

a. Why are solubilities often disregarded? Especially in cases like these, where solubility is low across the board.
b. Quick explanation for calculating predicted water solubility? eg. 2.54e-02 g/l into a readable number.