I would be prepared to bet alot of money (if there was somewhere to bet this) that 60%+ have got there homepage set as one of the Google sites. I also bet that 60%+ of them have got the google toolbar. So why do they?
To be honest I can't think of a reason to have a homepage set as google because there are much more useful pages like NetVibes. First of all you can search and you can pretty much fully customize the page, I think the only thing they really stop you from doing is making it look bad!!!
It is an excellent site you really should check it out. http://www.netvibes.com