Except that SATs measure something real (intelligence), so unless outright cheating and bribery are taking place, it will continue to be a good measure.
Is a someone who scored a 2300 after years of test prep necessarily more intelligent than someone who couldn't afford test prep or didn't have access to it and still scored a 2000?
"When researchers have estimated the effect of commercial test preparation programs on the SAT while taking the above factors into account, the effect of commercial test preparation has appeared relatively small"
EDIT: and to make it worse the college board charges exorbitant prices for everything involved in the process - it’s ridiculous