Because it's simple and sweet. Chocolate is straight up nasty, and Strawberry has a bit of a zest to it. Cookies and cream has little cookie chunks, but if I'm eating ice cream I generally don't want a crunch. Mint choco can be alright, but you have to be in the mood; it's definitely not an any occasion ice cream. But vanilla is just simple and sweet. No crunch, no zest, it's not chocolate which is always a plus, and it works for any occasion unlike mint choco chip.