Because the majority of the folks that have built up 1/2 tons for camping/exploring are realizing their payloads are surprisingly light so you're seeing more and more folks step up to 3/4 and 1 tons.
Myself included
It's funny. GVWR has always been a thing.
Seems folks in general only seemed to really start paying much mind to it in the last couple years. Hence the lean towards 3/4 and 1 tons of recent. I cringe every time i see a Tacoma with a loaded FWC or similar on it, wayyyy over the limits. Response usually: "Nah, they told me i just needed airbags and E rated tires" ummmmm That's not how math works! hahaha
Browse the classifieds and you'll see Tacomas and half tons for sale over and over again, and usually have verbiage along the lines of "Moving up to....", etc..
You'll almost never see a 3/4 or 1 ton for sale with someone saying "I want a smaller truck" just saying
Half tons have their place in the world, but built up and loaded with gear isnt it.
That's my unsolicited .02