One might think of businesses when discussing spreadsheets, but all people can find use for them. Teenagers are no exception to this. For example, if a teenager is working part time, they can create a spreadsheet to keep track of their salary and hours. They can also use it to manage their grades and averages in school. If they're supporting their family they can use them to keep track of spending in grocery stores, restaurants, or rent.
An example of an allowance spreadsheet (source)