I've worked on hundreds of computers over the years now and never worn a static discharge bracelet or ever had a problem from a component damaged by static. Dropping tiny screws however . . . yeah, that comes up pretty often.
Damage may be gradual and not immediate that would link static electricity to component failure.
From Wiki: "ESD in real circuits causes a damped wave with rapidly alternating polarity, the junctions stressed in the same manner; it has four basic mechanisms:
Oxide breakdown occurring at field strengths above 6–10 MV/cm.
Junction damage manifesting as reverse-bias leakage increases to the point of shorting.
Metallisation and polysilicon burnout, where damage is limited to metal and polysilicon interconnects, thin film resistors and diffused resistors.
Charge injection, where hot carriers generated by avalanche breakdown are injected into the oxide layer."
Note we are talking about months perhaps even years before the breakdown will manifest itself as failure. Even when a component is failing, you may not recognize it as hardware failure. Perhaps your computer crash a bit more often now then before or perhaps your program takes just a bit longer to run (due to errors that are being corrected).
If you look at the modern MOSFET, the amount of volt to puncture the oxide layer or damage the poly is very very very low......as in way way way lower than a typical micro ESD that you would not feel.
I used to design this shit a long time ago and I am pretty much paranoid about ESD. I ground myself (and keep my self grounded) every time I open up the case.
I do agree about the tiny screw....I keep extra around just in case.
Found another article on ESD:
http://www.howtogeek.com/262313/is-static-electricity-damage-still-a-huge-problem-with-electronics/