Data Retrieval

Data is presented in a much more accessible way with a spreadsheet than with a database. A spreadsheet puts data on a grid. That data can be accessed and edited on the fly. A database must be queried for data that can then be put into a grid style but not with the same on-the-fly editing features of a spreadsheet.

Speed

Spreadsheets can be ready for data entry much faster than a database. They are also better for small projects that will not be consistently ongoing.

Presentation

A spreadsheet is much more useful for a presentation because the layout is designed to be looked at. Most spreadsheet software has built-in graphing technology for generating eye-pleasing graphs.

Formulas

While you can retrieve and calculate with data using a database, a spreadsheet makes retrieving a certain range of information and plugging it into mathematical formulas incredibly simple.

Worksheets

Spreadsheets are excellent for speculating with worksheets. For example, you can create a spreadsheet of a yearly budget, alter and estimate numbers and gain a perspective on the year's budget easily. It makes no sense to build a database for speculation.

Source:

Comparing Databases and Spreadsheets for Storing Data

Spreadsheet or Database?

Spreadsheet vs. Database