What's there to risk? Career-ending injury? Name five guys who faced something like that because they came back to college.
What else is there to risk? Diminished skillset and the risk of "being exposed?" Reed doesn't have an artificial skill set. The NBA already knows he's a terrible defender, but his actual skills will only get better (passing, shooting, playmaking). He could become a legit top 5 pick next year, win POY, and truly contend for a national title as the best sophomore in the country.
So really, what exactly is the risk? I'm not buying it.