I kinda have that in boeren.nu. But my reasoning was that you can't be everything to everybody. A farmer might enjoy reading about tractors and cows, whereas a mechanic couldn't care less about the cows. I could make it easy to add interest to your profile, but only 20% of my visitors are logged in.

Also, while I certainly think of Google when I build things, I think of my visitors quite a bit longer. I always look at Google as the company that tried to replace me with their silly Google+ communities, as well as the company that sends me 40% of my traffic.