Faking a breakdown in a travel lane takes more personal time and is harder to work into the daily schedule of a commuter, so the cabal would have to pay the person more. Littering is blatantly illegal so there’s higher risk for a hypothetical operative. If I see someone dumping nails then I’m getting the plate number and the cops will be more interested in that report than about complaints of slow drivers. Only some state’s cops even look for passing lane misuse as a ticketablle offense.

It’s also about plausible deniability.