Why does any company spend money on building a browser? Microsoft provides a range of different development tools and programming languages for web development

Why does any company spend money on building a browser? Microsoft provides a range of different development tools and programming languages for web development. There is the modern stuff such as ASP.NET, Silverlight, etc, but lets not forget VBScript, ActiveX, etc, the latter not widely supported by other browsers. Microsoft has more to lose technology wise by dumping its browser than the other companies do.