aspnet_compiler - Security benefit
With ASP it was so easy to update web application - open it in notepad and you are done. Developers found it handy, IT folks not..
Then came ASP.NET 1.X - each change must go through build process to take effect. Developers hated it, IT folks liked it...
Then came ASP.NET 2.0 with new compilation model which brought back in place change and run without build required. Developers started to fall in love with it and IT folks got frustrated again
But wait! there is handy tool Aspnet_compiler.exe that gives IT folks even more power. It can precompile the whole ASP.NET application to binary format - even ASP.NET markup thus preventing not only from changing but even from viewing the markup
Cool, huh?