Configuring Haystack pipelines through YAML makes it easier to set up a question answering system, allowing for quick tweaks, parameter management in production, and distributed execution. YAML is particularly useful for conducting experiments as it allows for easy adjustment of pipeline components without modifying source code. By defining components such as Readers and Retrievers, and pipelines that chain them together, users can create complex neural search systems using a configuration file. The use of YAML also enables the deployment of Haystack pipelines with a REST API, allowing for easy import, modification, and export of configurations between experimentation and production environments.