The reason this is happening more and more is because teams are bumping up against the limits of synchronous communication. Especially when teams get large, and everyone has an expectation of immediate response the whole thing falls apart.
What's really needed is a communication platform that is geared towards asynchronous communication but integrated deeply with chat apps like Slack, Hipchat etc.
That's Bitrix24 point - chat plus tasks plus file sharing plus intranet plus client management in one place
People often say that other people expect an immediate response from im. Why not establish some sort of SLA so you feel free to ignore them into it's convenient?