Blending data from multiple sources is necessary when visualizing daily data in a way that allows for manipulation of everything as one solid bunch of data. The new data blending functionality in version 0.20.0 of Cube.js simplifies this process by providing two approaches: retrieving data as an array of query objects and defining a special cube within the schema. These methods allow for easier application of time granularity, finding seasonal patterns, and tracking correlations between channels. With data blending, developers can write less code, simplify their application logic, and build more creative visualizations.