Also prevents unexpected shocks to the buttocks upon sitting.
Directly grounding shouldn't be particularly risky though. It's not uncommon to have a metal desk touching a grounded but not double-insulated chassis or dangling USB cable. And I get the impression that electrical systems are engineered so that users aren't touching live contacts when plugging things in - maybe less so in the case of US plugs.
That said, an RCD/GFCI would help in either case, and might have in the cases of electrocution by faulty phone charger, where current presumably travelled through multiple wires in the USB cable alone.
Directly grounding shouldn't be particularly risky though. It's not uncommon to have a metal desk touching a grounded but not double-insulated chassis or dangling USB cable. And I get the impression that electrical systems are engineered so that users aren't touching live contacts when plugging things in - maybe less so in the case of US plugs.
That said, an RCD/GFCI would help in either case, and might have in the cases of electrocution by faulty phone charger, where current presumably travelled through multiple wires in the USB cable alone.