It does have a really easy way to extract your conversations as a log file though. An OSS version of irccloud you could just "apt-get install blahblah" with may have stemmed the rise of slack, at least in companies.
I expect this niche will be filled by Matrix in the near future. Host a Matrix homeserver + Riot.im web UI, then employees can use Riot mobile apps and any Matrix-supporting client.
For the record, I don't like Slack very much. I just disagree that IRC or IRCCloud are acceptable alternatives.