Political games - meaning, games with more than two players where you have wide discretion to help or hinder specific opponents - naturally bleed into real life. To have a loyal friend in these games who lets you win at their own expense, is a good strategy - you'll simply win a lot more games that way. Grudges carrying over from one game to the next becomes a natural part of play too - what else could dictate who you let win, if you end up in a kingmaker situation?

Politics has a habit of infecting everything. If you are determined enough to win, even games like Monopoly or Catan with relativelt modest political elements degenerate towards Diplomacy (or Nash's "So long sucker"). That's why in modern game design, designers try to limit the scope for politics to the absolute minimum, so that any game can be enjoyed in isolation without a metagame of grudges and off-table alliances.