I believe in the power of a good vocabulary. It makes you a stronger writer, allows you to express yourself much more clearly, and makes people more likely to respect your opinions as those of an educated, well-spoken professional. As a bonus, it’s good for a few (secret) laughs when dealing with pretentious people who like to use big words to belittle you (and often use them incorrectly!).
It only makes sense that I start with this particular word, as it directly relates to what this site is all about.