Its a japanese culture thing, dango are a type of sweet treat. The "translation" of this for a westerner would be "candy is only for kids".(Which is not true at all, and I don't know any adults today who think like this)
it's like Japanese Curry Rice being a kid's meal.
Globally, people just eat it as a regular meal, but in Japan, it's usually only ordered for kids as a treat.
(That's why the curry is sweet).