Acid base titration curve
In the case of strong acid-strong base titration at equivalence point with the addition of very small amount of titrant (like a drop) the pH change is very large. That means the range over which indicator changes its color is likely to be passed in a drop of titrant, resulting in a sharp end point.

Whereas in the other cases the change of pH at equivalence point is less dramatic and there will be a smaller change in pH at equivalence point. So, the indicator will change its color slowly resulting in a wider end point.