I'm not sure traditional metal-tipped pub darts are a particularly great example of an ideal kid's toy either.
Safety concerns can sometimes seem over the top but, if you look at "dangerous toys" lists with a modern eye, they mostly do seem like things it makes sense to pass on.
I would expect most of the injuries from the forbidden sharp lawn darts to have been to the head and/or shoulders? To 'poke a heart out' you'd need the victim to be laying down on the ground, which kids do obviously do, but presumably a little less when they see things raining down from the sky.
With a normal dart you poke an eye out. With lawn darts you poke a heart out.
Also many darts for kids these days are plastic.