I think it's just that it's interesting to look at critiques of political systems. Adam Smith doesn't have the same name brand when it comes to Capitalism that Marx does when it comes to Communism, so it's easier to see posts about marx and communism more generally. I find it interesting, personally, to see how different the modern day conceptions of these two schools of thought are from their origins, and how they contrast with the views of their originators.
That is, indeed, interesting. I think a great deal of these divergences can be traced to how capitalism (and, to some extent, communism) developed after WWII and during the Cold War -- especially after 1970's. Another factor worth noting, is how Marx is so strongly associated to capitalism (despite his critiques and propositions) to the point that even A. Smith sometimes gets overlooked haha.