The main grounding for board, drives, and the case itself is through the supply. In some cases the mounting plate the standoffs are placed on is made of a non conductive material. Look at some custom modded cases to see how that comes into play there at times.
The standoffs not only secure the board inplace but generally isolate any exposed leads(+positive) from coming into contact with a ground source. The problem many see is forgetting that different boards will see different bolt patterns such as comparing micro atx models or server boards to the typical full atx model.
Any grounding seen with straps going to the fastener holes assumes that some additional grounding is done there. You''ll see those used for esd reduction while not being the primary method of ground. If you look at some Antec Cobra round ide cables you will see the extra ground wire there while the drives will still work without that secured. That also offers some additional esd protection.
The standoffs not only secure the board inplace but generally isolate any exposed leads(+positive) from coming into contact with a ground source. The problem many see is forgetting that different boards will see different bolt patterns such as comparing micro atx models or server boards to the typical full atx model.
Any grounding seen with straps going to the fastener holes assumes that some additional grounding is done there. You''ll see those used for esd reduction while not being the primary method of ground. If you look at some Antec Cobra round ide cables you will see the extra ground wire there while the drives will still work without that secured. That also offers some additional esd protection.