Fallout: New Vegas and Neverwinter Nights 2 designer Nathaniel Chapman has taken to his blog on the official Obsidian Entertainment website in order to discuss video game realism and how experienced designers will intentionally implement mechanics that don't feel realistic in order to ensure that the gameplay remains entertaining. Fallout: New Vegas is even used in a couple of examples:
First - game designers primarily ignore or devalue realism because their primary goal is rarely to construct an accurate simulation of a real world. At their core, game systems are sets of rules that encourage and discourage, or reward and punish, certain choices within the game versus others. In establishing both what choices players can take, as well as the rules effects of those choices, designers are generally attempting to create a system which a) avoids "dominance" b) provides opportunities for players to differentiate their strategies based on the decisions they take, and c) give players opportunities to make "good plays" in response to opponents (be they computer or human controlled). Thanks, RPGWatch.
As a very basic example, take armor in Fallout: New Vegas. Wearing Light Armor has strengths (you move faster) and weaknesses (you absorb less damage). Wearing heavy armor has the opposite effects. Heavy armor does not dominate Light Armor, even though it performs better at its core functionality, because there are cases in which moving faster is more important than absorbing damage.
For a more complex example, because the game uses subtractive DT, low DAM weapons are disproportionately affected by DT. So, for instance, if a creature has 5 DT, going from a 6 DAM weapon to a 7 DAM weapon doubles your damage (your actual damage goes from 1 to 2). Whereas, if that same creature had 0 DT, going from a 6 to a 7 DAM weapon is only a 1/6 increase. This is an example of how you can encourage the player to make "smart plays" - when fighting an enemy in light or no armor, you are encouraged to use your highest DPS weapon regardless of its DAM. Whereas, when fighting an enemy in heavy armor, you want to select a weapon with enough DAM to significantly overcome its DT while still having enough DPS to deal substantial damage over time. When combined with the other properties of weapons (range, rate of fire, spread, etc.) you end up with an interesting matrix of choices in which players are encouraged to find the optimal weapon for any given situation. No weapon is dominant, players can select from a group of weapons they like based on their own personal playstyle, and there are opportunities for players to maximize their effectiveness through smart play.