Well, as it turns out, Lara's bust is a result of a mistake. Artist Toby Gard, one of the people in charge of designing Lara Croft, was toying around with the dimensions of the character. When setting the dimensions of her chest, he slipped with his mouse and increased the boob area by a cartoonish 150 percent.
And apparently replaced them with oil-change funnels.
The rest of the (male) crew immediately asked him to keep it that way, solidifying a stereotype about video gamers that we have not been able to shake in the 15 years since. And the rest is video game history. To quote the team, "Gard's accidental 'one-fifty' design made picking out a marketing strategy remarkably easy."