My understanding, albeit somewhat limited, is that generally amperes are a larger issue than volts in determining what sorts of electricity is dangerous. (Low voltage high amp circuits can't initiate sufficient amperage through the body to be dangerous in this way due to ohm's law but could still kill you through other means, such as burning you, but high voltage, low amp circuits are far less dangerous.)
Cap discharge? One story was the Robert VandeGraaff got the idea for his generator from a Boston printing plant, where the metal body of an ungrounded newspaper press on a wooden floor would give dangerous shocks to anyone approaching closely. If a machine is many meters across, and charges itself up to many tens of KV, the body capacitance may store lethal (joules) level of energy, e.g. 50KV at 1000pF.
Because it can kill you, that's it.
Electrostatic motors(capacitive) are older than electromagnetic(inductive), but using way more voltage than current means touching it will kill you.
A lot of people have died from industrial plastic bags electrostatic charge with friction, so it now uses wire to ground it.