The egg has been a symbol of new life and fertility for thousands of years. The hare also stands for fertility, also known as the companion of the fertility goddess Ostara. After the egg-free winter, birds and hens start laying eggs again - another sign that spring draws in. This is said to have led to the custom of searching for eggs. Since the hens were free to run around at that time, they also laid their eggs somewhere. In order to use the eggs, people had to search for them.
Another assumption is that giving eggs was a pagan tradition to Ostara and was punished by the church. In order not to be caught, the eggs were no longer handed over personally, but hidden in fields. Family and friends had to go looking for the eggs. Seen in this way, what we still do today at Easter.