I track many things in my spreadsheets and grouping is a lifesaver. When I decide to track the TV series that I have watched by Season and suddenly there are 1000 rows in my spreadsheet, it would be almost impossible without grouping together first alphabetically and then by show as a secondary/subgroup. This makes it much easier to find what I am looking for and not be bombarded with however many rows in each spreadsheet.

This is one of the two main things keeping me with google sheets at the moment and I would love to fully switch over once Sheets here get some good UI/Quality of Life updates!