A lowpass filter is an empirical hack, not a gold standard. It has multiple disadvantages; rather than being "responsive," it adds latency to the initial input for no good reason, and it affects both rising and falling edges equally, again for no good reason. It also requires the addition of unnecessary physical components.

For instance, taking a look with a scope, if you observe that the signal stops bouncing after 3 milliseconds, it would be pretty safe to accept duplicate keypresses with a 10-ms guard interval.