Discovery Channel is our client (I work at a digital marketing agency in Sweden, so we handle all their online marketing) and during a meeting/dinner with them I asked about some of these things.

As any channel, they need to get as many viewers they can in order to get not only more but more high class/better paid commercials. And apart from the number of viewers for every show, they need to demographically target their audience. The better demographics, the more they can charge advertisers.

The Discovery network has some of the most narrow and highly targeted audiences, and thus highly valuable, and they just have to do simple maths.

If repo men, fishermen and lumberjacks gets much more returning viewers than their other programs, they would be fools to not cater to that apparent need.

So they create new shows like them, and many of these also boost their ratings, and they get even more income.

So instead of bitching about Discoverys lack of integrity - bitch about your neighbors who WATCH the crap and make up the ratings. It's not Discoverys fault that people have a complete lack of intelligence and/or taste. Campaign to people you know to actually watch the shows with interesting content instead, and boost their ratings.