Question

why we are not able to see in dark ?

Answer 1

The main problem is that there is no light in the dark and we need light to see.

Human eyes are adapted to see best in the daytime. We sleep at night so unlike nocturnal animals our eyes don't have the enhancements to capture as much light as possible in the dark.

Some animals have an extra layer in the eye to capture more light, while other have more cells that work in darker environments but there's always pros and cons to each adaptation. So an enhancement in one area would give us a disadvantage somewhere else. Humans are very well balanced to survive in a wide range of conditions so having better vision in the dark would mean another aspect of our vision will be reduced.

Answer 2

we cannot see in dark because there is no light to be fall on objects and reflect to our eyes so we can't see anything in dark