people love to talk about a game being realistic or not realistic without asking whether more realism = more fun. Usually the answer is no. Doing collision detection on every bullet on every frame is a cost that may or may not be worth it, depending on the overall design of your game. "Games take shortcuts" is really flattening the discussion and acting like the game developers don't know these things that the very smart blogger knows, when in reality, game developers know this stuff and make conscious design decisions. Most games are not designed to be scientific modeling programs, they're entertainment products, governed by questions about entertainment value, not simulation accuracy. Plus in real life you're not going to receive a network packet that says "a bullet whose trajectory will hit you in the skull will reach you in 0.7 seconds" and give cheaters enough time to auto-duck with a script. Even if you can afford to do collision detection on every bullet on every frame, there are many other reasons why it might not be a good idea. Hitscan is a design option, not something that's "right" or "wrong".