Language acts both as a diffuser of culture and as a stabilizer. On one hand, a common language unifies a culture. However, when people from different areas speak the same language, culture spreads more easily. So, there’s greater cultural homogeneity among all English-speaking countries and among all Spanish-speaking countries than there is between English-speaking countries and Spanish-speaking countries.
When nations share a language, business is easier because there’s no need for time consuming and expensive translations.
Often, people studying languages choose the ones that are most useful in interacting with other countries.