The reasons why to learn Spanish are manifold and range from general ones, such as the mere ‘size’ and spread of the language to special individual interests, for example in Spanish literature.

The numbers mentioned in relation to Spanish are impressive:
Spanish is spoken in 44 countries worldwide (English in 112, French in 60, and Arabic in 57), and is the third world language after Mandarin Chinese and English.
329 million people speak Spanish as their native language, it is the second most spoken first language after Mandarin Chinese.
Spanish is the official language in more than 22 countries worldwide, it has official status in the three American states New Mexico, Arizona and California, and is one of the six official languages of the UN.

In a globalised world where distances between countries and cultures are shrinking, it seems to become more and more important to learn a second language:

In the work environment, employers increasingly favour bi- or even multilingual employees and in order to expand your business successfully towards the Americas, to be able to speak Spanish is one of the top priorities.
In everyday life when meeting other people and cultures or during holidays, you will not have the same great experience if you cannot communicate with your hosts or people you meet in your city or during your travels.
Being able to speak and read Spanish also opens doors to deepen your personal interests in the Spanish culture that shaped the world for centuries. Artists like Picasso or Miró, Cervantes or García Lorca, Almodóvar or Buñuel, Dalí or Gaudí they all seem to be much closer and easier to understand.

And last but not least some practical facts: Spanish belongs to the Romance part of the Indo-European languages, together with French, Italian, Portuguese, and Romanian whose origin is Latin. Due to this origin (Indo-European and Romance) there are many words in Spanish similar to words in English, German, Dutch and even more to French or Italian. With the latter two Spanish also shares many grammar rules. Moreover, Spanish is a very phonetic language; if you read a word in most cases you will also know its pronunciation. Hence Spanish is quite easy and very suitable to learn as a second language, and it will also expand your knowledge about your own mother tongue.