The GRE Computer Science exam was pretty heavy on theory and systems. This made sense for 1990, when CS departments were heavier on theory and systems. It has grown less relevant as the field of CS grew to encompass additional areas.
Thus, CS programs stopped requiring it, so fewer people took the exam, so the ETS decided to drop it.
I understand the rationale for dropping the exam, but it's the last academic endeavor on my resume. I've got a ton of work experience since then and many of my projects would be worthy of today's buzzwords. My lament is that only forward-thinking advising professors would see the value in what I have done.
Note that no professors have actually been tracked or harmed.
Thus, CS programs stopped requiring it, so fewer people took the exam, so the ETS decided to drop it.