Why would I care about ABET accreditation for a CS program? It's not like CS is a regulated field that requires a national standard. That would be like complaining that a schools History department isn't accredited.

For things like medicine, professional engineering, legal, etc... I care that those degrees are from accredited programs, but not CS. What I do care about is that the school itself is accredited and legally allowed to confer degrees.

For what it's worth: CalTech does have ABET accredited programs in Chemical, Mechanical, and Electrical engineering. So, they must not feel that ABET accreditation offers much for a CS program.