Many years ago, I was manager of a video arcade. When the power supplies failed, we replaced them with generic switch mode power supplies.
However, I found out that without grounding, just the leakage from parasitic capacitance in the power supply was enough so that the chassis would float at 1/2 of the line voltage, 60V here, and with enough current to give you a palpable shock. I discovered this by touching the chassis of two games, one with a broken ground lug on the cord, the other properly grounded.