Well, there is always the exception to "the Norm"Actually it's always analog. What you interpret as "abrupt" or "sudden" or "just like that", in the analog world, there is always some "transitional curve". The "transitional curve" may not be able to be "recorded" or "captured" by our perception or our ability since our brain cannot capture things like the oscilloscope can, but it's there.
In order to have "just like that" in the real world, the energy required is "infinite". Like a step response, on paper, it's abrupt. But in the real world, there is no such thing as a "step response" since it would require "infinite" amount of energy.