I don't think Americans understand the purpose of the rule. It is to prevent a 'hack-a-Shaq' strategy to prevent goal scoring. Because a PK is an almost-guaranteed goal, defenses have to play looser in the box to avoid it, which makes for more scoring opportunities (and is more fun to watch). It also makes for an issue of flopping to sell a PK, but refs have gotten much better at not falling for it.