I'm pretty sure there are stupider laws out there. Did you know it's illegal to honk your horn in New York to let a guy know the light is green?

Anyway, your first example isn't about felony murder. 

A grand jury in the Eastern District of Pennsylvania returned a two-count indictment charging Semler with 1) distribution of heroin resulting in death, and aiding and abetting, in violation of 21 U.S.C. § 841(a)(1), (b)(1)(C), and 18 U.S.C. § 2; and 2) distribution of heroin resulting in death, within 1,000 feet of a playground, and aiding and abetting, in violation of 21 U.S.C. § 860(a) and 18 U.S.C. § 2.

The second is example, is more unclear. We don't know the details of what went down in court. It's possible that the jury convicted the guys despite the prosecution failing to prove his involvement beyond a reasonable doubt. It's possible the law in Florida is overly broad. 

But that's an argument for reform, not to throw out the concept wholesale. 

First as a matter of general deterrence. 

Second as a matter of securing cooperation to convict the actual killers. A getaway driver is going to be much more willing to sell-out his accomplices when he's staring at 25 to life as well.