Here is my experience.
You may refer to my profile and My application for citizenship at the following link which I posted some time back.
http://goo.gl/oaPjIl
In fact I did not mention about my grassroot activities in my previous post. I am holding an office bearer position (Holding Vice Chairman Position, Volunteer work ) in one of the Community Group with in CC. I am also an active member in RC. I have contributed approximately 8 years of volunteer service to CC and 2 years of volunteer service to RC. I have received 5 years service award.
I usually spent approximately 25 to 30 hours in a month in RC and CC activities. I am an active volunteer.
Initially when I applied for citizenship. I just mention as an Executive Member of CC in citizenship application. After approximately 7 months my citizenship application along with my family rejected. Having lived here for two decades, I was bit worried. So one of my RC friend suggested me to request help from our MP who is also Senior minister of state. I approached our MP and our MP knows me well. So our MP considered my request and wrote a letter to ICA. After about a month I received my rejection reply for the appeal through out MP from ICA.
I understand ICA has very stringent criteria now. Having a PR and contributing to Singapore (Some do contribute) and applying Singapore Citizenship is a privilege and not an entitlement.
Involving in Gross root, it is a voluntary work. We involve because of satisfaction we get as there is not much benefit.(Except school admission which I do not need as my kid already in O level)
I involve because I enjoy doing. Helped many people made many friends. When I walk on the road, many familiar people. Many say hi and smile to me. I am not a stranger. Many residents from other races who I helped once, remember me well and calls my name and say Hi when I see them on the road. Happy faces
So based on my experience, involving gross root activities may not increases the chance of getting citizenship.
There are many experts in this forum. Correct me if am incorrect.