I mean with the UNCs of the college world taking a Cardale Jones approach ("We didn't come here to play school") - What's the harm to the players? Especially in the one and done world.
HS kids with potential can capitalize, make some life-changing money and see what happens - all without risking injury or worse exposed lesser-talent.
You named two pretty impactful HS -> NBA hoopers (as in first ballet HOF type players), but there was also KG, Jermaine O'Neal, TMac, Dwight Howard, Amar'e Stoudemire, etc. If you pull up a list of names there seem to be more who had long (if not highly impactful) NBA careers than didn't and I'm a casual NBA follower.