The TSA has a stated goal of getting a substantial majority of passengers through pre check, which I think is good policy; getting rid of the dog and pony show of "regular" TSA screening (at least for most passengers) is a Good Thing. So no, I won't be writing a lettter encouraging TSA to limit precheck to Very Important Passengers like me.
There does seem to be a common misperception that pre check is about making the security experience faster for frequent travelers. That was never the goal; it is a side effect during the multi-year rollout of the program as well as an enticement to encourage more passengers to sign up. The goal is some combination of making security faster for everyone and reducing TSA costs.
(What does this have to do with Delta? I think this belongs in the safety and security forum.)