"A spreadsheet is an interactive computer application program for organization, analysis and storage of data in tabular form." [1]
We drew grid charts in elementary school for a huge variety of reasons, but we never did them on a computer (because we didn't have computers back then. Spreadsheet software was (first) valuable as a calculation tool because it replaced tedious accounting "worksheets" (also noted by wikipedia) but now I'm curious what percentage of spreadsheets use the mathematic functions at all. Most of those I see around software development are simply ways to organize text.