There’s ratings gold in them there gold shows! Two weeks back, “Bering Sea Gold” (10 p.m., Discovery) was the highest-rated series debut in that network’s history. And last week, its cable ratings got even higher, reaching more than 3.5 million total viewers. There was a time when that would have been considered a paltry network audience. But those were in the days before every show had to compete with hundreds of other choices.

In fact, the proliferation of channels and the fracturing of the market have resulted in the cookie cutter sameness of the cable viewing experience. “Gold Rush” begets “Bering Sea Gold”; “Jersey Shore” begets “Jersey Couture.” Cupcake shows breed like rabbits. Or the Duggars. And so it goes.

This wasn’t how it was supposed to turn out. When cable emerged, folks anticipated that more competition would bring more choices. Even quality. And for a while it did. In the early 1990s, some even argued that because networks like A&E and Bravo broadcast ballet and fine arts programming, PBS had become superfluous and unnecessary. Boy, that was a long time ago.

With broadcasters scrambling to win so small a piece of the audience pie, many have become risk-averse. If you propose something entirely original and it fails, you could lose your job or your chance to produce another show. But if you imitate or blatantly plagiarize an existing format, you stand a chance of getting a respectable rating and you live to see another day.

Given the difficulty of breaking out of this rut, you have to commend the broadcasters that still make a stab at originality. But don’t expect them not to be punished for their efforts. HBO’s “Luck” has not found an audience to match its critical acclaim. According to the Nielsen website TVbytheNumbers, “Luck” not only failed to crack the top 10 cable series last Sunday; it didn’t even make the top 100.

• Kristen Wiig plays the demented fan of a local band that uses a cat to garner YouTube attention on “Portlandia” (9 p.m., IFC).

Tonight’s other highlights

• A disturbed woman sparks a hostage crisis on “A Gifted Man” (7 p.m., CBS).

• Marisa Tomei explores her roots and looks into a tale about her grandfather’s violent demise on “Who Do You Think You Are?” (7 p.m., NBC).

• On the trail of a black widow on “Grimm” (8 p.m., NBC).

• A grieving daughter claims to receive a divine diagnosis of her mother’s cause of death on “Blue Bloods” (9 p.m., CBS).