The problem with paper...
Printing out a physical document and passing it between parties creates significant costs and delays.
Fraud and Operational Risk
Data input errors are common and committing fraud is as easy as printing out a guarantee's details underneath a bank's letterhead.
Tracking and Reporting
Only a single party can know the guarantee status at any one time creating ambiguity and uncertainty throughout its lifecycle.
Lack of Standardisation
There is no standard for bank guarantees making them difficult to review and negotiate for everyone involved.