You are right, I hadn't. So I went and did. Seven enforcement letters over the course of a week is what I found. I could find you the evidence for seven enforcement letters about every seventy seconds along any stretch of freeway near any major city.
So my use of "never" was inaccurate; in a tiny fraction of the cases, somebody from the FCC attempts to enforce the regulations. It's still such a tiny fraction as to have negligible effect, and I doubt that the stern warnings about possessing/using cellphone jammers will be followed up with enough enforcement to make a difference there either.
And I stand by my claim that the govt in general would have at least more respect if they didn't write laws/regulations that they won't enforce in any meaningful way.