Why does it really matter if the setting is more-or-less consistent with now or with recent history, vs older history or extrapolated near-future, or speculativ

Why does it really matter if the setting is more-or-less consistent with now or with recent history, vs older history or extrapolated near-future, or speculative advanced technology (sci-fi), or magic aka "sufficiently advanced technology" (fantasy)? I'd think the part of "subject matter" that would matter, would be what the problems are. Are the characters trying to stay alive, trying to keep their jobs or get promoted, trying to find the best parties to go to, trying to sneak around while avoiding their parent, etc.