Mr Elliot is spot on. The prime reason is the decreasing number of travelers. We don't care to just stay on the West coast so tend to travel on the eastern side. We spent 2 weeks in Cd Valles as friends there and the only other visitors were a French family for 2 nights. Then to Palenque and people were German, Belgium and Aussie surfers in a Tuk-Tuk, one night a couple from Vermont. Horgar Infantil, a Spanish couple, now in Oaxaca it is the Belgium folks again, Dutch and British. These folks follow ioverlander as most are full time travelers. We momentarily meet a couple from Oregon who actually owned a restaurant near us for a while, but now live in Chapala.
The Mayabell camping area is 1/3 the size it was and last time at Chimulco it was almost deserted(3 years ago) as compared to 10 years ago being in the overflow area. Folks don't appear to be starting traveling (as we all know that it so terribly dangerous down here)and the rest of us are getting older.
You must admit also that driving around is not without its hassles and quite stressful and the costs are increasing. The first day from Reynosa cost us $180 in fuel and tolls.
I could go on.