I think it's still the majority of developers that first deal with databases outside a cloud environment and then want a managed version of it in their environm

I think it's still the majority of developers that first deal with databases outside a cloud environment and then want a managed version of it in their environment (which btw, Amazon does offer in RDS Postgres/MySQl, but it's their forks that have these problems). And being behind the bleeding edge is problematic at least these days that databases are incorporating great features, but the bigger problem is incompatibility and subtle differences. Those are the truly annoying issues.