Why are old impact craters often difficult to identify?

The impact craters are hard to identify because of the following reasons such as-

Continuous weathering and rapid erosion- The rocks on earth rapidly undergoes weathering and erosion, since millions of years ago, as a result of which the impact craters are affected, because it removes the features that could help us in determining that it is a crater. This erosion are caused by the agents such as wind, water and ice. The different parts of craters becomes hard to recognize.Tectonic activities- The plates movement at the convergent, divergent and transform boundary has been continuously taking place and the plates are destroyed and new plates are created. Due to this, the previously existing craters are removed from the earth's crust. So it has become difficult to find the old craters.