RC and RL time constant
One time constant is 63%, not “done”, which is why quoting RC as the settling time is wrong by five times. The same two parts are also a filter, whether that was the intention or not.
1 ms
10 kΩ × 100 nF = 1 ms
63%, one of them
1 ms
95%, three
3 ms
99%, five
5 ms
Corner
159 Hz
The same curve, from the other end: Charging through a resistor.
One time constant gets it to 63%, which is why quoting RC as the settling time is wrong by five times: call it settled at 5 ms. The same pair is a filter with its corner at 159 Hz — anything faster than that is being attenuated whether you meant to or not. For a button, it swallows contact bounce under about 3 ms, and most switches chatter for 1 to 5 ms.