Reason:
The incresing rate the vampire population has caused the Vanilla scented stuff to sky rocketed. Vampires need the Vanilla to cover the smell of blood.
Other reasons:
1. Many have tended to focus on the pleasant childhood memories associated with the smell of vanilla, its comforting milky warmth.
and
2. Others have noted the appropriateness of vanilla scents for the 'softer, more caring' zeitgeist of the 1990s – as opposed to the thrusting, bullish 80s, when the fashion was for perfumes so overpowering that restaurants had to ban them because customers could not taste their food.
Thank you to Emzoisweirdsowhat for the suggestion!