Here's why:
* Frequency: It's used to create adverbs from a huge number of adjectives. For example, "quick" becomes "quickly," "slow" becomes "slowly," and "happy" becomes "happily."
* Versatility: It can be applied to a vast range of adjectives, regardless of their origin or structure.
* Simplicity: It's a straightforward and easy-to-remember suffix.
While there are other adverb suffixes like -wise, -wards, and -ways, they are less common and often have more specific meanings.