I had an one year Internship at "JTAS Laboratoriet" in my youth 1979-1980 and was told about problems with ESD and components.
It started when the big long distance telephone exchanges became digital (they kind of where before that too), using First-Gen 4000 CMOS IC's.
It was observed that the first versions would die within 24 hours of a Module (Dual Europe size Cards - 6U Rack high) being exchanged from unboxing a brand new and plugging it in
So the Lab got a big amount of those Dead Modules back from the Technicians, located the dead IC's - opened those and put them under a Microscope. Here they could see some Very big Craters from the 'Punch-Through of the Electro-Static-Discharge'
This made Ericsson change the packing to including an Anti-Static bag + the Technicians where instructed in how to handle the Modules correct, when changing them .... => big improvement ...!
.... BUT not a total solution - now it took about a month after being replaced before the new Module had died
So the Lab did the same analyze on those -> Now the Craters where smaler than the with of the 'Tracks on the Silicon Substrate' -> the IC worked until the remainder of said Track burned over from the current running through it ....
This inspired some of the big IC manufactors to start adding Protection Diodes etc. to the I/O of the IC's in the 4000A and 4000B series - further reducing the problem .... But you still have to take care.
I was told that the Strap works nicely - but the problem can be solved without using it.
1) Always touch the 'GND' of the equipmet / PCB you're about to handle, before handling the PCB / IC / MosFet.
2) If you should give a Device (IC/Discrete) to another person - Do NOT put it into their hand !!!! - but drop it into their hand @ a distance about 200mm / 8" .... Why ? - well the device can't contain any charge that can dammage it + the distance between the persons are too big for a Zap between them.
There are a few more - but I have never worn a strap and had not had any IC's gone bad (from ESD).
Discrete MosFet Transistors - I had some, until we used 2N7002 - then many (probably 10-20%) => we changed to using the 2N7002CK that has internal Zener Protection of the Gate => problem solved.
Sorry for the rant ....
Per