The ending of this excellent story clearly identifies the universal issues faced by teenagers, whatever historical time period they are based in and wherever they are. It is this final chapter where Ponyboy reflects on what Johnny writes to him that makes this book so enduring and so popular, as everybody is able to find some connection with it that resonates. Note what Ponyboy writes in the last two pages:
I could picture hundreds and hundreds of boys living on the wrong sides of cities, boys with black eyes who jumped at their own shadows. Hundreds of boys who maybe watched sunsets and looked at stars and ached for something better. I could see boys going down under street lights because they were mean and tough and hated the world, and it was too late to tell them that there was still good in it, and they wouldn't believe you if you did.
Ponyboy identifies the pressures facing teenagers, and the way that Johnny's experience and his own experience is something that is not unique. The division through class or geography or other factors into different groupings and the pressures of society force boys to become "mean and tough" and believe that there is nothing "good" about it. This is the central problem facing teenagers everywhere that this novel identifies and explores.