This was 2013. I wonder if a few years made a difference.
Every site off the southern side of the ring road had 4-5 tour buses full of tourists, plus assorted individual cars. It wasn't crowded to the point of annoyance, but it was close. What was annoying was poor behavior by many tourists - stepping inside the chains and touching water at Geysir, going into the "caldera" of Kerid Crater, and going near the water at Reynisfjara Beach. All despite many signs in many languages. And poor tour guides chasing the idiots back to safety.
I'd guess if we went north, it would have been relatively quiet, but we only had 4 days, so based out of a flat in Reykjavik.
I only had time for the touristy stuff in the immediate vicinity of Reykjavik. I would like to go back and see it more intimately.
Weird.
Anyways, I hypothesize that some TV shows from taking place in Iceland brought a lot of attention to the landscape which was capitalized on by the Tourism departement.