The airlines have no incentive to care. Since the TSA has no method for tracking who has been issued an SSSS and who has actually been secondaried, they have no knowledge of whether the individual was screened at the gate on a connecting SSSS. I have yet to see a GA that complains about no initials/scribbles from TSA on any BP, and I never present my connecting BP to the initial TSA at the originating airport.

Yet another notch in the BS of our current security regime.