Board Thread:Episode Discussions/@comment-25086462-20170412225621/@comment-734582-20170608063003

Bambusek wrote: Yeah, and not only kids. Look at Hiashi, he is before his sixty, but looks like he is closer to seventy. I think it's part art style, part deliberate choice. Itachi did tons of extremely questionable stuff, most of it as a teenager. But even during the Uchiha Massacre he already looked 20 or older, and during most of the series he looked 30.

I say artstyle because Kishimoto himself said that he had trouble getting Sasuke's age right, since he tended to draw him looking too old. So it could simply be that.