Here's why:
* Frequency: It's used to form adverbs from a vast number of adjectives, making it incredibly common.
* Ease of use: The suffix is relatively simple and straightforward to apply.
* Consistency: It consistently attaches to the end of adjectives to create adverbs (e.g., slow + ly = slowly, happy + ly = happily).
While other suffixes like -wise (-clockwise), -ward (-forward), and -ways (-someways) exist, they are far less prevalent than -ly.