Google just loves to waste your time. A close friend of mine interviewed there, was flown out to Mountain View, and one interviewer showed up to the interview over 30 minutes late, with only about 5-10 minutes to spare. He didn't get the job.
Seems like a lot of engineers there get the job after many months of (unpaid) preparation and years of interviewing many times. I can understand doing this for one's dream job, but my issue with the whole thing is that you don't even know what group you'll be placed in, which is in stark contrast with the interviews at most other companies. I'm not spending months practicing Leetcode questions and going through some hazing interview process only to potentially be placed in some boring group working on something super specific and uninteresting.