Disclaimer: not all "older" films follow this but from what I've seen, the majority do.

In older films (earlier than 2010), I have seen that a lot of teenage characters are played by actors / actresses in their 20's.

Two notable examples are:

• Spider-Man
  Tobey Maguire (26) plays an 18-year-old.

• The Amazing Spider-Man
  Andrew Garfield (27) plays a 17-year-old.

Why were older performers cast in these roles? Were actual teenagers deemed unworthy?

In many films, I have seen that a lot of teenage characters are played by actors in their 20's.

Two notable examples are:

• In Spider-Man, Tobey Maguire (26) plays an 18-year-old.
• In The Amazing Spider-Man, Andrew Garfield (27) plays a 17-year-old.

Why were older performers cast in these roles? Were actual teenagers deemed unworthy?