The reasons are varied, many of which are well articulated in the article, but the most notable throughout various workplaces I've worked at, there's been a hesitance to jump on MS web frameworks in fear of a repeat of silverlight.
Silverlight burned a lot of small businesses hard, almost everywhere I've worked has had a silverlight horror story of a project they experimented in it with only for it to languish. So now they either have some outdated dependencies they'll never update or had to re-write it back into something else.
Even without silverlight concerns, most .net places I've worked have very much been legacy focused. This might be my own culture fit at interviews so I end up with places with lots of legacy of course.
But these giant legacy systems already have a plethora of mixed web technologies from ASP.net webforms, asp.net MVC, through .net core MVC, and many others. The willingness to add another different technology into the mix isn't relished.
For small companies, the cost of migrating older projects to new technologies is a significant burden which gets ignored for as long as it can be reasonably done so.