Visual Basic, the great-great-great grandchild of Microsoft Basic for the Altair, the company’s first product, is the oldest.
/crosses fingers
The other reason is they likely wanted to have lots of developers use their language, so by killing VB off, the most popular language in the world at the time, they thought they would be able to claim a lot of .NET users very quickly. And of course, Java was being used as an alternative to Microsoft's stuff and C++. Both of these show stupid standards.
Python and Ruby, for example, were created with the idea of having a beautiful and useful language, and not by Microsoft for enterprise use, nor become popular as a big company enterprise alternative to Microsoft's offerings. Learning an open-source, beautiful language that isn't run by a big corporation for enterprise use is just refreshing.
See Java's Cover: http://paulgraham.com/javacover.html
Still, I'd be happy if they killed off VB so that I wouldn't have to deal with its syntax and retardations. Working in an MS environment I can only ask for so much, but at least with C# my loops get braces.