That's the purpose of Ryu. Ryu is meant to always meant to be completely focused on training and finding stronger opponents. Its better to compare Scorpion with Sagat. Both started out[or atleast in 2 for Sagat] wanting revenge {Scorpion because Sub-Zero killed him. Sagat because Ryu scarred him} Capcom knew the revenge plot was an inevitable dead end [look at where Scorpion is now] and changed Sagat from wanting revenge to a fair rematch and abandoning his hatred [he actually called Ryu an old friend in his SF4 ending] and as a result became the most well developed character on the roster.

Teken>Mortal kombat>street fighter

Damn! Then what have all the other guys and gals been doing all these years?

Ken is pretty much the "I'm pretty much Ryu's rival. So if he's here I got to be here as well.", Guile wants to take down Bison and Shadaloo for killing Charlie [which they seem to making less clear cut] Chun-Li wants to take down Bison and Shadaloo for killing her Father, Cammy is a member of MI-5, Abel wants to find out his past, Honda wants to promote Sumo as the greatest fighting art, Dudley wants to bring dignity to the fighting circuit and find exotic roses for his Garden and regain his family's prized jaguar automobile and his family's fortunes. Vega because he wants to rid the world of ugly people, Rose wants to eliminate the evil in Bison, Adon wants to beat Sagat and become the new King of Muay Thai,Balrog because Bison pays him. That's a few off the top of my head for the moment.