@dw - my best guess is Compliance and Regulatory reasons/reporting + Fraud prevention/Monitoring. Less easy to cheat or for accidental errors to not be picked up when on the Bank systems.
May not be the case for every division or role, but there are some where either mistakes happened, someone did something they shouldn't, moving/stealing money, etc. that would've been caught faster on the Bank system.
If it goes on for 2+days, harder to trace and fix.
Not sure if still the case, there also have been Corporate Tax Incentives paid by various states and municipalities for bringing people back into offices to reinvigorate downtowns and support the local and national economies. That's why they are so hot on the Badge Swiping. There is only one vendor now (bought up the competition) for Badges, who sells the aggregated data to Employers and reports same to local/state govts.
OR.... Management are huge Megalomaniacs who enjoy sitting in their Glass Corners surveying their Fiefdoms of Minions across the filthy, germ-and-crud infested Open Layout. #powertripping