The DU Lounge

Caffeine is more soluble than any of the phenolics or esters that are the principal flavor components.
So, by extracting with cold water, they can remove the caffeine without drastically changing the test. (It still does lower the "richness". The process is far from perfect.
The used to use methylene chloride until the public started gaining awareness of the many issues around chlorinated solvents.
The industry converted en masse to water, but kicking & screaming.
Caffeine for stay awake tablets is still extracted from low quality coffee beans using solvents but usually something line methyl ethyl ketone, which is a safer solvent than methylene chloride.