This makes me wonder, what is the difference in technologies? I never used IRC to be honest, was it downloadable software or was it web based? (I'm not that young I swear, I'll be 35 next week - I just didn't do chat)
Popular GUI-clients would be Colloquy on Mac, mIRC on windows and XChat on linux. Just download one and see for yourself; Freenode is a popular network for hackers of all kinds, QuakeNet is the network for gamers (and also happens to be the biggest with ~60k users online at any given time).
It's just done well. It has stood the test of time, and seen nearly 30 years of development in multiple, competing irc server products. A lot of rivalry and different views and attitudes to certain strategies.
IRC is amazing. Servers are linked as leaves to hubs, or as hubs, linking to other hubs or leaves. If the network splits (one server goes down, breaking the tree) it can be quickly relinked to secondary or tertiary servers, restoring connectivity. For its time, and even to this day, it is an impressive protocol that is not only fairly easy to implement from a client perspective, but a very scalable chat server architecture.
