Thanks for the list, it's quite a few, some apps more known than others.
But if they settled for a .im domain, I think it is because the keyword was available for regfee (which is still rather high in this ccTLD). It doesn't mean they would buy a .im at aftermarket price, from a domainer. See what I mean ?
Just had a look dnsaleprice, at first glance I don't see any chat-related domains in the list of reported sales. Specifically, none of the domains you quoted are in that list either. Assumption: all are regfee purchases.