Your account manager is an exception, and your argument is a false equivalency: just because you know of a non-technical person who has experience with IRC does not mean that all nontechnical people have experience with IRC. Indeed, the trend is most likely that people in non-technical roles have less experience and exposure to such tools.
HipChat is more than an IRC server - it's a fully searchable web-based chat archival system, as well as a file transmission and sharing app backed by S3. It's also fully mobile-compatible and will do proper message routing to multiple devices owned by the same user, as well as temporary message caching/retry if your device is unreachable when a message is sent. etc etc. The list goes on.
None of it impossible to replicate in-house, but I dare a non-technical person to replicate HipChat's stack.
Google doesn't exactly have an "IRC on crack" product though? Also, I find GTalk's routing to be spotty when it comes to multiple devices - it's quite common for me to receive messages from coworkers at night and have them route to my work machine instead of one that's active on the GTalk account at home.
Nowadays we use GroupMe for things that must be read in a timely manner. It'd be nice if we could use GTalk for it (this is a Google Apps GTalk account, not a public one).