Here's why:
* Suffix: A suffix is a letter or group of letters added to the end of a word to change its meaning or grammatical function. Examples include "-ing", "-ly", "-ness", "-ment".
* Prefix: A prefix is a letter or group of letters added to the beginning of a word to change its meaning. Examples include "un-", "pre-", "re-", "mis-".
So, a suffix is always added to the end of a word, while a prefix is always added to the beginning.