Why should you want to be Bilingual?
I think that you should want to be able to speak many different languages.
learning a foreign language is the entry gate to learning about ,and getting to know the various cultures of people who speak that language, consequently, expanding our horizon and teaching us more about our own culture which is the core of what we are. The more languages we learn and speak, the more we know about ourselves. To me personally, next to many other reasons, this is the most valuable aspect of learning foreign langues.
Most of us are well beyond the stage of brain plasticity that would allow us to be come truly bilingual, so wanting or not wanting is a little beside the point.
That said, there are many established benefits to learning additional languages. Alongside the ones other people have mentioned, learning a language can help stave off dementia as you grow older: https://www.newscientist.com/article/dn24537-learn-another-language-to-delay-three-dementias.