Maybe the author should consider this possibility:
Startups don't use it, because: - there may be other technologies that are better for the job - startups rarely care about Microsoft's heavy marketing which alone can convince a lot of managers to use a technology just because it's from Microsoft
And one of the worst things is that it's a Windows technology, say what you will, but if you want .NET you need Windows, and pay a zillion $-es for license. Yes I know there is Mono, it's very close, but no cigar, it's like wine, it lags.
But in the end I want to ask a question too: What could .NET bring to startups that other languages can't?