In Excel you have to option to delete worksheets as soon as you realize that you don't need it anymore, this can be easily done by right-clicking on the tab you want to delete and select this action. However, sometimes you will see that this option is not enabled.
This option is disabled when the workbook is shared, so more people can collaborate to the file at the same time, this situation is shown in the title of the file, this will include '(Shared)'.
To disable the shared property of the workbook go to 'Review' ribbon and select 'Share Workbook' option.
Then, you will see the list of users that have the workbook open, once you uncheck the 'Allow changes by more than one user at the same time...' box and accept, the workbook will lose its shared property.
After this, you try again and notice that the 'Delete' option is enabled again and ready to use.
Consider that the 'Shared Worksheet' option is not anymore recommended in newer versions of Excel, use co-authoring instead.