I think popularity of roaches as pets sucks in the US compared to what it should be. I've not noticed a huge downturn. It has always sucked. There are many wonderful species that just never sell. If there has been a decrease, it's in the culturing of people, not the culturing of roaches.
I'm not surprised to hear the BCG forum is inactive. There was a brief moment when we were converting Orin's historic Allpet Roaches Forum (see archives) over to this newer software and we invited the UK-based BCG folks to join and collaborate with "the US hobby". But their hobby practices forbid sales (they decided to go with Olivia and her new roach forum at the time--now the BCG forum), which is unfortunate because the world runs on money and, for me at least, monetary exchange actually enhances the interactivity of the hobby--makes it more interesting. People are more motivated to stay in it if the costs of time and maintenance are partially compensated by the freedom to participate in occasional sales without fear of being looked down upon by "credentialed" hobbyists getting paid to look at the genitalia of male roaches through microscopes and writing papers on it. And the act of assigning costs to roaches gives them value against other species (if only in our minds). Eventually they come crawling back to us for livestock, and pay for it, because it's cheaper than a plane ticket to Timbuktu. Now, that's a simple history of the hobby the last several years. Zephyr has come along in this time period and infused quite a bit of time and energy into the roach hobby across many (lesser) forums. There are, unfortunately, more dealers of roaches than passionate hobbyists. You look at the big tarantula and mantis forums out there and that role is reversed. I think this is the most telling comparison of the "pet" roach hobby to similar hobbies. Of course, we all know that roaches are significantly more interesting to keep as pets than tarantulas or mantises with their various behaviors and variety of available species. Unfortunately, we still have to deal with the pest stigma in this country. We have few hobbyists, a large percentage of which have spouses that are dispassionate about roaches, and who may have visitors to their homes that are even disgusted by roaches. For example, my children have friends that think our home is the most interesting place in the world, and yet their parents have heard about our "interesting" pets and will not come through the door. These are the same germ freaks that can't name ten insects or plants from their backyards (perpetuating a pattern of ignorance that has only generally increased with each succeeding generation of Americans). C'mon, you can't even begin to share the beauty of an organism known as the Florida Skunk roach with a person that doesn't know or care that the tree in their yard is a plum tree, despite all the small fruit they sweep up before the birds, bugs, etc. have had a chance to feed on it.
Society and regulations.