The significance of API gateways in microservices architectures lies in their role as a central point for managing API traffic. They serve as intermediaries between clients and microservices, handling tasks such as request routing, authentication, and rate limiting. API gateways help simplify communication, enhance security, and improve overall system performance. By providing a unified interface for accessing multiple services, they enable developers to control how data flows within a microservices environment, thereby facilitating scalability and easier maintenance.