I'll second (or 3rd, or maybe 5th) the idea that they're available because people bought something they THOUGHT they wanted, then realized they didn't.
Same deal for LCP's and LC9's. The Concealed Carry fad shot sales through the roof, then people that were either new shooters or casual at best shooters ("I own a pistol, I shoot a couple boxes a year" types) bought these hard-to-shoot pip-squeak handguns, took them to the range, and hated the way they shot.
Really can't have your cake and eat it to. Either you want a gun that's fun to shoot, or you want a gun that's concealable and easy to operate. The SP-101 isn't any bigger, but the extra weight and DA/SA trigger makes it a joy at the range. I don't think the new owner turn-over rate for SP's is nearly what it is for the LCR's, but the LCR's move faster right now because of the CC Craze.
Why I don't have an LCR? They're butt-ugly. Why I have bought several of them used? Because I can flip them easily, buy from someone that changed their mind, and sell them to the next sucker that is mistakenly buying a DAO Superlight as his first handgun.