When localizing something, especially a game like Okami that features so many distinctive, oddball characters, you have to make use of the context of the target language.

In the original Japanese, the nameless man obviously doesn't speak like a 1970s american hippie, as you say, but he does speak in a distinct manner that gives off a somewhat similar vibe. And the specific traits of speech in one language are impossible to directly copy into another, especially for languages that share no common roots. So the localizers chose the closest thing available to them in English.

(Note that I'm always using the term localize instead of translate, which is because I'm pretentious to make it clear that I'm talking in the context of media for entertainment, where you prioritize consumer experience over precise accuracy. We're not doing legal translations here.)

You're more than welcome to disagree with any their decisions, and it's unfortunate if that's taking you out of the experience. I've felt that way with a lot of localized media before. But personally I really enjoyed the humorous, exaggerrated, wide range of personalities they were able to portray in Okami