That's interesting. I often think about why airlines bother to have curbside checkin anymore. Elites generally have short checkin lines inside the airport, and I would think that non-elites would not be enthusiastic about tipping the curbside checkin people in addition to paying checked baggage fees (although it does help quite a bit when the non-elite checkin lines inside the ticketing area are long). Nonetheless, I still see many people using curbside checkin at many of the busier airports I frequent.