Probaly 1st used for power gating and not for logic, low level logic that does not need speed.
If contact resisitanc eis made low enough these could be put in series to provide better MTBF for the case of stuck switch on.
Low frequency logic will also be applicable for this.
Blog Make a Frequency Plan Tom Burke 17 comments When designing a printed circuit board, you should develop a frequency plan, something that can be easily overlooked. A frequency plan should be one of your first steps ...