Did you notice that many people are still using ASP? This is somewhat strange due to the popularity of.NET. Why are they still using the classic instead of the new and powerful ASP.NET? First of all, .NET has XML-based components, better language support and user authentication, and a huge set of new controls. It can also increase performance by running code that is already compiled. However, .NET code is not backward compatible with ASP code, making transitions somewhat time consuming.
In ASP, if you have a script block that is marked as "runat = server" and this block contains a function, you are allowed to include executable code outside the scope of the function. ASP.NET does not allow this and instead uses the code-behind technique. There are a lot of pros and cons to this technique. Another strong side of classic ASP is the threading model. The threading model is Single Threaded Apartment (STA) and the older one's worker thread is contained in its own STA. This ensures compatibility and also increases performance. ASP.NET uses the MTA (Multiple Threaded Apartment) which forces developers to take extra precautions.
So why do people still use ASP instead of the more powerful.NET? Well, one cause would be the knowledge. You need a lot more basic knowledge to work in.NET than you need in classic ASP. Even low level things seem hard to do in.NET. There are a lot of things you should learn and you should have a lot of free time if you really want to master.NET. Many people recommend classic to average users because they do not need any of the new features and the performance is almost the same. There are also a lot of applications, tips and tricks, and tutorials available for classic ASP. Only large corporations truly have to work with ASP.NET to gain scalability in their technology.