They don't let you "install" an extension, the `CREATE EXTENSION` command is just enabling an installed extension for a specific database. There are a ton more

They don't let you "install" an extension, the `CREATE EXTENSION` command is just enabling an installed extension for a specific database. There are a ton more extensions than Google Cloud SQL or AWS RDS support. Both of them for example don't have the often used hypopg extensions which allows you to hypothetical create an index to check whether it's used for your queries and see how your execution plan changes. Building indexes for large databases can take a lot of time.