That's really not a great comparison, especially since browser-based social media and browser-based chat services (e.g. Facebook and its chat) are what killed services like AOL/ICQ, before later moving into mobile apps. Pigdin was fairly niche even back in the early 2000s. Facebook is bigger than any of those services ever were, because Facebook did a way better job or attracting the average person. My family used email before Facebook, for example.

Given all those things with hindsight, it makes perfect sense for browsers to have long lineages and it makes perfect sense why standalone chat services mostly died out.