ThunderCavalier said:
There aren't a lot of backstories for fighters beyond "They fight because why the fuck not." is there?
There are but they are largely isolated to movies/etc, the games themselves do a terrible job of storytelling. At least Tekken tried to have a story. In case of Ryu, a lot of his personal story is based around defeating the primary antagonists like Sagat, M.Bison and finally Seth.
The SF2 movie (the only good one as far as most fans are concerned) is the one where we get an insight into Ryu's "idle" life. He wonders the world (barefoot like a real man), gets his money from street fights (duh?) and/or doing people favors and helping the weak. That's...about it

Also Sakura keeps running all over the place blurting "Where's Ryu? Anyone seen Ryu? I'm looking for Ryu!" in her cute little school uniform.
Ryu is comparable to Goku in the sense that he doesn't really live for any other reason than to seek friendly fights, never kill (or even seriously wound) anyone and keep getting stronger...but at least Goku had the balls to settle down with a woman and have kids -_-