Why doesn't someone actually ask hackers to design a secure(er) CPU, OS and programming language from the ground up ?
Why doesn't someone ask doctors to design better people from the ground up?
As others have pointed out, security analysis and secure design are different fields, though related. And practical security analysis - finding and exploiting vulnerabilities - is very different from practical system design and development. "Hackers" is irrelevant here; those are simply different jobs.
And there's no such thing as a "secure" anything. Forget that concept - it's meaningless. Even "more secure" is only meaningful in context.
And we already have CPUs, operating systems, and programming languages designed to be more secure than the popular ones against common attack vectors. We have capability CPUs (Intel i432, IBM's i version of POWER). We have Orange Book A-level certified OSes. We have languages like Ada, Erlang, and Haskell.
For the most part they haven't seen wide use1 because of cost. CPU security features cost performance. OS security features slow down users, developers, and administrators, and require more highly-skilled, less-common staff. Language security features require less-common programmers, who can charge correspondingly more for their labor. And businesses have a huge investment in existing systems which they are disinclined to simply throw away.
Even in an era when businesses can suffer large, expensive, embarrassing losses due to security failures - think Target, for example - the economics don't favor switching to equipment with more security features. Target can't afford the capital expenditure to switch to a POS system written in Erlang and running a formally-verified OS. For one thing, they'd have to build it themselves, with staff they trained.
1The IBM AS/500 / i machines are successful, but their numbers are dwarfed by x86, obviously.