I posted about the lack of traditional air rifles for sale in these classifieds just the other day on another forum, IMHO it's not just with air guns, take a walk through the classified adds on Facebook Market place for vehicles, you'll find a distinct shortage of the most reliable vehicles and a over abundance of problem cars and SUVs, late model BMW's, Mercedes Benz, Audi's, Chryslers and Jeeps, Nissans, and Isuzu's and the like for cheap money.
I look at these air gun classifieds in the same way, the more Traditional Springers, gas piston, pumpers, and Co2 guns are not there because owners tend not to get rid of them because they shoot well and they are fun, there's allot of PCP guns and gear for sale because people got caught up in the power, range, accuracy, and ease of shooting rabbit hole, then they experience the leaks, break downs, lost filler connections, the aggravation of being worn out from hand pumping or the breakdowns of expensive compressors, or hauling air tanks around with them and they say screw it, I'm not having fun anymore, I'm going back to my break barrels as soon as I can get rid of this PCP albatross around my neck.
That's my story and I'm sticking to it.