Well, some people in Japan do. Wouldn't say all. And I think more are just ignorant. I definitely agree this story would make more sense if Naruto and Sasuke were actually gay or at least bi, since they never came off as "best friends" at all, due to Kishimoto's shitty writing.
It's worth noting that most of the world's modern homophobia exists thanks to the Victorians. After a few prominent individuals made themselves known and they figured that gay was a thing, that stopped all the "bro-fection" between men, because they didn't want to appear to be gay. And as you can imagine, this didn't lead to good treatment for actual gays. So, yeah.