Can’t understate how much people want the nice/fancy/pro device too. It’s hard to lure people off MBPs to generic PC laptops or chromebooks but an iPad Pro + magic keyboard is shiny enough.
Not just lower support cost, but much higher security bar at a lower cost too. Having been at the same fund, and other big banks, that’s an important consideration. Strong MDM, yubikey support if you want it, decent app sandboxing, etc. gives a lot of security control in a nicer manner than on a desktop OS.
Finally, I think the Office/GSuite issue depends so much on usecase and who’s using which bits of each suite. Gmail is so much nicer than Outlook, but GDrive horrible organizationally compared to OneDrive, while GDocs collab beats O365, etc.
