Putting a 0.1 uF cap directly across a set of switch contacts can lead to degrading switch reliability and lifespan. The very low resistance of a switch contact at the instant of first conductivity can result in discharging the capacitor at current levels that are rather high and could be well over the switch contact ratings. If it is deemed necessary to use capacitor filtering with a switch it is advisable to also use a resistor so that the RC time constant gives the desired delay or filtering action and the R saves the switch contacts.

Michael Karas