Even at a 100 person company I knew, half the organization used gchat and half used jabber/webex connect. Each side had champions that spent a ridiculous amount of time trying to convert everyone to one platform, and last I checked they still hadn't succeeded.

There are gui clients that support both protocols (i.e. I think Pidgin does) - why not just write a plugin that allows to cross-communicate between the two?

As time goes on I get more and more disillusioned with solutions that begin with "why not just write".

Nothing excites me more than having to think about supporting yet another codebase deployed to non-technical people who will undoubtedly cause more bugs than thought possible and open more JIRA tickets about it with increasingly vague title names.

At some point Slack or [integration of choice] is cheaper than having an internal engineering team to write half-baked communication solutions.

Incredibly true; for something as simple and necessary as messaging, the company I work for has:

1. A company-wide and approved solution (proprietary) that's very buggy.

2. A jabber server someone threw together so everyone could use their client or choice.

3. Google chat (through various clients).

4. MSN messenger / Skype.

And they all get used by different people for different things. It's very frustrating. Switching to a new thing would be a non-starter, probably (and we couldn't move to Slack anyway, but that's another issue).

Indeed. It took us about 4 years after officially switching from AIM to Skype to kill AIM, and then with Gtalk/Hangouts we're just now starting to try to kill Skype.