Necessity to learn Chinese?

I won't hurt.
You'll find a whole new circle of friends, and probably have a lot more fun.
My Mandarin is really rusty now, but it worked out great for me when I used it a lot for business in the UK)

Thank you much

I found that there is no need to learn Chinese in Singapore. I lived there 12 years and only needed it with my in-laws (who don't speak English) - everybody else swiftly switches to English as soon as a non-Chinese-speaker joins.
It also down't help that Singaporean Chinese do not speak Mandarin (= standard Chinese) at home, but the dialect of their ancestor's home province (Cantonese, Hokkien, Teochew, Hakka, etc.).

It's not harm learning another language esp if u think u have the interest.  I guess here in sg you have no problem finding people who speaks English. I personally felt learning languages is something that you need to have the interest . Not expecting u to be expert overnight but simple words like thank you =Xie Xie , how are you = ni hao ma. Good bye =zai jian and sorry =dui bu qi.  Haha. .I'm sure it will amaze those who starts speaking mandarin to u.

I would say Chinese is a good to know but not a must. Most of Singaporean will know English unless you are communicating with the older generations.