$2 here. They figure it'll guilt-trip you into answering the survey. If I sent them a survey asking who what when where and why with a $1 would they take the money and send the answers? I'm guessing take the money and throw out the rest, like me.
I've filled out ENOUGH surveys.
Some air filtration people wanted to give me a vacation for 2 if I listened to a demo and filled out a survey. They didn't like it when I told them that I was the homeowner but I didn't have a job. Then they insisted that my GF be there to listen as well. I told them to bugger off. Too much hassle.