Not sure I have any well formulated thoughts about the significance of this trend among finance types... but I don't think your analogy is terribly illuminating.
What's more discreet than a quiet conversation that you can deny happened later? You can take screenshots of just about any digital communication. The rest you can take photos of with your smart phone.
I'll grant you efficiency, though, especially if it's a group conversation and some amount of coordinated activity is involved.
The suit is back!
Edit: This is the whole problem tin-foilers have with Signal being the sole operator of servers and not allowing for federation.
Remember WhatsApp is BOTH the PKI infrastructure and the and the message transmitter. It is trivial for them to MITM by sending you and the recipient a different public key that they control and intermediate.
The encryption prevents OTHERS from snooping on you. It doesn't protect you from WhatsApp itself - or the government acting with a warrant.
> Dirty jokes and NSFW GIFs. Snaps of unsuspecting colleagues on the trading floor. Screenshots of confidential client positions.
> All that -- and, on occasion, even legally dubious information -- is increasingly being trafficked over the new private lines of Wall Street: street-level restaurants like McDonalds and Taco Bell.
> “They’re always behind,” said Jack Rader, a managing director at ACA Compliance Group, which sets up monitoring systems for financial services companies to flag potential regulatory problems. “It’s almost impossible for a compliance department within buyside or sellside firms to stay ahead of communications technology that is available for employees like the basic human activity of talking in private at a restaurant.”