It makes a big difference for legibility which font you pick. But I see what you mean in that, if the font is "just fine" (not trying to be fancy or, say, in futuristic style for a game or something), then why bother making yet another "just fine" font as Google has done here? There's already so many sans-serif fonts that no person could tell apart if they don't see them directly side-by-side and are asked to spot the difference. For this reason, I also wonder why this release matters at all