I think he is simply developing slower. He will get better in time. I think some people are way over blowing the numbers. Smart can easily handle the ball as a PG we see it every time he actually gets the opportunity. And of course a players numbers will improve when they control the ball and offense so sure if given more PG duties his % will go up. Even the playoffs when C's had to use IT off the ball Smart handling the ball did well and shooting was better. The assist are never high in BS' system so there isn't a need to focus on that stat. It is all about simply playing the best current player. IT is best current PG. When Smart passes him in overall game impact then Smart will get the call. C's aren't big on development through playing time while the main goal is always wins. Smart will have to prove he is better to get more time at PG over IT.
TP for the most logical post
+1
He still has potential and can certainly improve, but I don't think it's as simple as "he needs more time". He's not that athletic, doesn't have much speed, doesn't have much of a first step and can't shoot. Those aren't things that are just easily remedied by time.
When he first came into the league the knock on him was that he just used his size to bully his way past people. He wasn't a very efficient scorer on that level either.
So while he may indeed make a leap (here's hoping), I wouldn't say it's a lock to happen. This might be what he is. A solid defensive role player.