Because if I don't do this then I could just use my normal google account. I would bet that they actually have measures in place to find out how many google accounts belong to the same person and to link them together internally. Nope. I just don't participate, too lazy.
look, I'm willing to be very understanding towards people who have no google account and do not want to create one, but if you already have a google account, you are just being paranoid and you seriously underestimate significantly what Google already knows about you.
A combination of having full access to your Email communications, plus your browsing history (Google Analytics runs on like 90% of websites or something) makes it very easy for them to know who you are, how old you are, who your friends are, what your interests are, where you live, where you go out, WHEN you go out, what hardware you have, what games you play and purchased, what you like eating, that you have a Pandora, and for how long you have it, and how much connected you are to the community, and so on.
If you think Google is going to learn anything new from answering this survey, well you're just deeply mistaken. What this survey does is to share some knowledge with me (and I cannot identify who you are anyway because you don't have to put your name anywhere, I have no access to your IP or anything else either) and the community. If you don't want to answer, fine, I am not putting on gun on everyone's head to answer, but you don't have to come with over-the-top excuses and conspiracies theories about Google sucking your whole identify from such a simple survey.
And if you were seriously at all concerned with your Privacy, you probably shouldn't use Google at all, have no Smartphone or no phone altogether, use Tor from different connections points every time you connect (using Tor from the same place every time is extremely unsecure), and encrypt every email communication to your friends, If you aint doing any of that, your whole info is just widespread knowledge for whoever is interested to pick it up.