OK, say you're a bank. The SEC states you need to keep archives of every discussion your traders have with anyone at any time (I'm simplifying things but you get the point). You keep getting massive fines because traders were whatsapping about deals
So now you've got several options - you can use MS Teams, which of course offers archival, compliance monitoring etc. But that means trusting MSFT, and making sure your traders only use Teams and nothing else. You can use a dedicated application for the financial industry, like Symphony or ICE Chat or Bloomberg, but they're clunkier than B2C apps.
And then the Smarsh (owners of Telemessage) salesman calls you, and says "your users can keep using the apps they love - WhatsApp, Signal - but we make it compliant". And everyone loves it (as long as no-one in your Security or Legal teams are looking too hard at the implications of distributing a cracked version of WhatsApp through your MDM...)
Edit: here's the install document for their cracked WhatsApp binary https://smarsh.my.salesforce.com/sfc/p/#30000001FgxH/a/Pb000...