What is why do guys like white nails?

It's difficult to make sweeping generalizations about why "guys like white nails," as preferences are subjective and vary greatly from person to person. However, here are some possible reasons, keeping in mind that these are not universal truths:

Ultimately, attraction is personal, and there's no single reason why all guys (or anyone, for that matter) would like white nails. Some might not like them at all, while others might find them very attractive for various reasons.