I'll also add that product analytics software is built more towards measuring depth of engagement: How many times has this user returned to our site? What is th

I'll also add that product analytics software is built more towards measuring depth of engagement: How many times has this user returned to our site? What is the average LTV of this cohort? What is cohort X's n-day retention compared to cohort Y? What features have correlation to those differences? Did this experiment lead to improvements in retention - 30 days later? Google isn't built to go that deep. Sure you can see that 3% of users have used feature X, but you can't really effectively dig in and see how upstream or downstream actions and events influence each other. Sure you can create some custom segments on a sessions/user level - but that quickly turns complex and unwieldy if you have several segments, cohorts and funnels. Also there are a lot of charts that are just plain better in product analytics tools. Retention charts, funnels and path diagrams are obvious examples.