Untealistic, no, but the issue becomes really apparent in titles that indeed aim for being as realistic and believable as possible. In a fantasy setting you have your typical magic ingredient which allows for explaining/forgiving a lot of stuff that wouldn't/shouldn't happen in real life, in sci-fi setting you have all the fancy tech to back everything up, and so on, but in a modern, down-to-earth settings writing is what makes or breaks that believability. Same goes for movies if we're at it, way more so than in video games.