Single-episode Blu-rays?! But -- why?
Basically, we live in the end times. Pretty sure it was prophesied in the Bible somewhere. You know, single-episode blu-rays, human sacrifice, dogs and cats living together... mass hysteria!
Seriously though, the low-cost deals offered at retailers during release week (I essentially got it for free, most only had to pay a few extra bucks) coupled with exclusive special features make these attractive to hardcore fans. Later on, more casual fans who would never consider buying a season set pick them up too: "Oh, yeah... I remember that show when I was ten. What the hell, it's only $15 bucks!" It's really a no-brainer for CBS. It costs them almost nothing to produce them and it makes their first week numbers look better on the Blu-ray sales charts.