"Smart" is a quantifiable hard limit. The problem with smart people is that as soon as they run up against a challenge/concept/issue they cannot immediately overcome, they get frustrated, because they "should be smarter than this!" Which often results in avoidable frustration/anxiety/depression.
You see this a lot. "Gifted" "smart" kids who coast through school for years, until one day they finally run up against something they cannot do and run away from it screaming. Simply because they're not "smart enough."
Where is the school program that let's the bullshit pseudo concept of "smarts" fall by the wayside and instead replaces it with an atmosphere where failure IS acceptable, and that you just have to work through the hard parts?
I have a kid. My wife's side is second generation "gifted." These people are absolutely obsessed with how smart they are/sound/come across, and get incredibly upset/frustrated/annoyed when they feel "dumb" (i.e. things are hard, they don't get it right away, or they make a mistake).
Unfortunately when I raise the issue of "hey, focusing on an intangible level of intelligence could be damaging [here look at this child research]" I just get eye rolls, because they're so deeply into the concept of how innately intelligent they are, they cannot see a less damaging way of living one's life.