Microsoft are trying to change how people think of their web browser. Edge is very important yet they are launching it without one of the biggest features needed in a modern browser, extension support.
But do you believe that more than 1% of web browser users install and use one or more browser extensions?
In 2013, this article[1] gave numbers of anywhere from 9% to 22% of users blocking ads, which requires an extension AFAIK. So, "yes". Even if those numbers are exaggerated due to skewed measurements, I'm pretty sure it's going to be more than 1%.
[1] http://www.forbes.com/sites/kashmirhill/2013/08/21/use-of-ad...
Not sure if it has Silverlight, but since we aren't streaming the 2008 Olympics and Netflix doesn't need it anymore I'm not terribly worried.