Tables can use a variety of data sources, however charts only allow tables as source data.
This creates a lot of mainteance overhead (and clutter in WP admin), because each chart has to have its own dedicated table as a data source. And the only way to filter the data table in the chart wizard is by manually selecting rows/columns, which is error prone/tedious. There’s no general filter options like “string contains”, “greater than”, “less then”, etc. This means your Table pretty much needs to be all the rows you want to chart. That creates a lot of permutations and turns into a mess quickly. Especially when you’re using custom post types and you want to have a chart for every post.
Supporting the other data sources for charts will open up the possibility to create different chart variations by pointing to the same data source but applying some filtering/transformation in the chart wizard/settings to be able to chart something different. That means 1 data source but many charts.
This provides value by significantly compounding the number of possibilities while reducing admin maintenance and keeping WP admin cleaner/simple.