Hiring a Flask-SQLAlchemy developer is beneficial due to their proficiency in creating dynamic, database-driven web applications. They understand Flask, a micro web framework that offers flexibility and fine-grained control, and SQLAlchemy, a SQL toolkit that provides an effective way to handle databases. Their expertise ensures efficient data handling, improved application performance, and seamless integration with other technologies. They can efficiently solve complex queries and provide robust, secure solutions. This combination of skills makes a Flask-SQLAlchemy developer an asset for developing scalable and maintainable web applications.