What the hell do those guys want to do with a 24bit-ADC?
Simple answer: "make the marketing guys happy".
There is one other reason to use a 24 bit ADC: the specs (drift, tolerance, error voltage, error current) are usually better) and you can get a bit better than with an ADC that just has the resolution you state (11 bits)

I do agree that with a 24 bit ADC, there is no need to read the 8 LSBs.

Erik