Imagine you have a system that ignores taps a substantial percentage of the time (either because it required more precise finger placement, or because that's life). Also most successful taps complete quickly, with only some having 250ms latency. Combine these two and most of time when nothing has happened after 250ms, it's because the tap failed to register and a new tap attempt is needed.

There's been plenty of research for decades showing that 250ms response time in UX is a noticeable slowdown.