Because you want to expand your cultural competency, critical thinking skills, and position yourself a top choice candidate for employment or graduate school.

French opens up a rich world of culture, history, and ideas that have influenced western and global culture for centuries.
It is projected to be the world's most-spoken language by 2050. This means more need for communication in French with a rapidly growing Francophone population.
In the business world, French is the second most important language for direct access to the global marketplace, in particular in Europe, Africa, the Middle East and parts of Asia.
In fact, Foreign Languages is the fifth most promising major for long-term employment .
In general, learning a second language helps you understand your own language and culture from a different perspective. Speaking more than one language is not only personally enriching and potentially life-changing, it also opens up many opportunities in the U.S. and abroad.