Isn't that like tracking down Al Capone for bootlegging liquor, and then only charging him with tax evasion?
In the case of Capone, it was just easier to prosecute tax evasion; "here's his bank balance, here's the tax we think is due, here's the tax he paid". In the case of shoplifting, plea-ing out a misdemeanor is probably easier than convincing a jury of a felony charge.
Like, all they probably have is a grainy video of the suspect. Are you convinced beyond a reasonable doubt that that's the person sitting in the defendant's chair? If one juror thinks "no, I'm not sure", then everyone who commited the crime goes free.
Also, realistically, $950 shouldn't be the threshold between a felony and a misdemeanor. That can't be a number that was adjusted for inflation. $950 isn't much money these days.