Often times it's valuable to have excel-style calculations or formulae based on other fields already set in Hive.
For example, if regularly had to run ad-hoc analysis on actions based on time spent multiplied by a custom field on each respective action, I would have to export it to CSV or Excel and manually add a formula.
If Hive had a new custom field type for Formula where I could define basic operations (math operations, referencing other fields, hard-coding values, etc.) then I could avoid the extra step and save a lot of time + effort.
Ideally, having this in Table Layout to start would be most useful and then adding support in new places from there.