the thing is, some people don’t have the sensitivity to appreciate what different strings bring to the table and are perfectly satisfied with your standard poly stuff
that being said, the strings is a matter of personal preference, looks & feel. I find different throws perform different with different strings, response wise at least.
oh and the websites that sell graou strings usually sell yoyos too
there is no official graou string shop, although you can probably get them from the xcube website too