My understanding of ESD is that there has to exist a path to ground for static charges to discharge. Take a MOSFET as an example that is vulnerable to ESD and packaged in a way to protect against it, as long as the component is free standing or none of the leads is connected to ground or a lower potential, I should be safe to hold it with my hand without taking any precautious. Essentially my hand and the transistor form an open circuit both sharing the same electric potential with no current. But it is a fact that touching sensitive components even when they are not powered or just being held by itself can cause damage through static discharge - for that I just can't understand. As if a plane can safely fly through a densely charged cloud (me holding a sensitive component), only until a lightning strikes through the fuselage on its way to reach ground (the component has a path to ground).
A drawing should help clarify my question. (A) A hand accumulates some static charges (5000V of static charges to ground). Assume the body is not properly grounded and the static charges on the hand have no path to go. A transistor has 0V or no static charges presence. (B) A finger comes in contact with the drain of a transistor. The drain is now 5000V above the source and goes beyond the maximum voltage rating. Thus the transistor is damaged. (C) All three terminals of the transistor come in contact with the hand at the same time. The drain, source and gate go from 0V to 5000V in parallel. There is no potential difference between the terminals and transistor is not damage static discharge.