Why not to expose SQL interafce or DynamoDB API directly to the client? ;)
While tools like AWS AppSync, Hasura, & PostGraphile accelerate initial development, the bulk of SW Engineering costs are adding new features & providing ongoing support and maintenance.
That said, there are uses cases where this might be a good pattern - e.g. limited distribution internal tooling.
Direct access to SQL is a great example of something that is not an antipattern. It's just one approach of many, with strengths and weaknesses.
In my use-case adding new features and support is the majority of eng work. We find Hasura is valuable here in reducing the cost of doing so - especially compared to traditional REST implementations.