I have four arguments as to why google are behaving this way with regards to this data. I’ve no idea which, if any, they operate by:
1. It’s actually crap and they don’t want their advertisers to know that their ads are sold based on crap quality data/don’t want the backlash of doing a poor job helping
2. Most people at google care a lot about privacy (either in the secret kept between you and google sense or the more common sense definition people seem to use on hn) and they don’t really think about this data as something the firm has/should release
3. They are afraid that if governments realised they had this data then google would be regulated or every minor security agency/random government department would be demanding access to it by law.
4. They strongly feel that surveillance by (well intentioned?) private companies is ok but by governments it os not.