What would be a reason for toggling gridlines on in a chart?

Toggling gridlines on in a chart serves primarily to enhance clarity in data presentation. When gridlines are included on a chart, they help viewers easily interpret and compare values against a reference axis. This is particularly useful in identifying trends, patterns, and specific data points, allowing the audience to grasp the context of the presented data quickly.

For instance, if a chart displays sales over time, gridlines can visually guide the viewer's eye, making it easier to ascertain how specific sales figures compare against one another or against benchmark values. This visual aid minimizes ambiguity, ensuring that the information conveyed is both accessible and engaging.

The other reasons listed don’t align as strongly with the primary function gridlines serve. Enhancing aesthetic appeal, while a consideration when designing charts, is not the main intent behind using gridlines. Limiting data visibility contradicts the purpose of gridlines, as they are meant to clarify, not obscure. Integrating external data also does not directly relate to the presence of gridlines in a chart, as this process focuses on data sourcing rather than visual interpretation.