Obviously it is a minority programme these days. But since the non-celebs are barely paid, it must be dirt cheap to run as a series. The house is used for a couple of celeb series, so they might has well fill it with non-celebs for a few weeks and let them disport themselves. They are still getting over a million viewers, and probably don't give a damn about the millions who used to watch it and have moved on.
As long as this series does not collapse, they will probably provide more of the same. Fishing round for models etc must be much cheaper than auditioning thousands and thousands of people, the tasks have become cursory and cheap - am I dreaming, or did a task once involve a helicopter? *- ; they have ditched live feed, so slashing editing costs, and have allowed for a raft of lucrative product placements. They seem to be keeping the voting up as far as possible by making sure the most profitable combination of people is up each week.
Of course, for those who understand the original concept of Big Brother, it is nothing like it; it is just another scripted reality show, but cheaper to do and with better viewing figures than Towie.
* edit: That was on I'm a Celebrity, where the tasks have also got cheaper.

Still, we won't be seeing any Africa swaps, or even bungee jumps, any day soon.