It's repeated enough that it's a conscious decision. Google offers good application platform, but locks in the data layer.
See AppEngine. Had (and still has) much bigger potential than heroku since the beginning. But where do you store data? Random stores with random limits.
CloudSQL is great? Backup/restore in CloudSQL is half baked. Multi master for MySQL is half baked. All these are very well solved with RDS, but Google wants to sell you 3 or 4 different data stores with different arbitrary limits.
AWS free tier provides a tiny RDS insurance for you to store useful data. Google cloud free tier? No standard SQL databases. Again, arbitrary locked in custom nosql with random functionality and usage limits.
It's spread out enough that it looks like a planned strategy to give an open computation platform but lock in the data, even at the risk of driving away potential new/small customers.