IRC was just a chat app, yet even though it didn't age nicely, was still seeing massive usage for professional communication up until lately. Is it only because

IRC was just a chat app, yet even though it didn't age nicely, was still seeing massive usage for professional communication up until lately. Is it only because of legacy? Hardly, new blood was pouring in constantly, the only hit it took was skype. Slack is simply disrupting this area by offering product which is up to date and doesn't need bouncer running (+ hundreds of other useful nice to have features).