Spreadsheets have transformed business. But there are limitations in what spreadsheets can provide. Once the limits of spreadsheets are reached, database solutions are needed. (See What is a Database) . Most business applications, whether bespoke or off-the-shelf, are based around some form of database.
Recently, some software developers have found that web technology can be used to make bespoke database applications much more affordable and usable.
Windows has many advantages and is nearly universal on PCs but it suffers from poor database support. In fact, Windows is really designed for applications like word processors and spreadsheets. There have never really been any standards for providing Windows database apps. The solutions that exist have tended to veer between the very expensive and inelegant. The solutions are rarely easy to set up and they often place many restrictions on the layouts of forms. The lower priced ones are difficult and expensive to maintain.
However, the software to create web sites has become very standard and sophisticated. The software components work well, and many are open source with minimal or no licence charges. Some developers have realised that it is now easy to build business apps around intranets. These reside on the user's server and are accessed through the browser.
Using intranets to provide apps provides many benefits.
You only pay for the development, not licences for a database engine
Traditionally, database drivers have had to be installed on every workstation. All that is needed to use the software from a new PC is to type the app's address into the browser.
And, of course, everybody knows how to use a browser.
Web software, especially the PHP programming language and the MySQL database engine are popular with developers and there are large numbers of developers available. This reduces being tied to one supplier.
Web technology is here to stay. The environment is stable and suppliers are committed to the future. Standards are not controlled by users, not companies.
Cost of development can be significantly cheaper than traditional methods.