Waste of resources:

It costs a lot of money to light up homes, public places, sports, and commercial places. Apart from the fact that taxpayers pay needlessly for this, the nation uses millions of tons of oil and coal to produce the power needed to light the sky. Meanwhile, the environmental cost of producing this energy is another worrying issue that can be discussed at another time. In the USA, 8% of its total energy is used for outdoor lighting, and out of that, 80% is used for commercial and public exterior lighting.— Darksky

Loss of historical and cultural value:

Astronomers are concerned that not only do they have difficulty reading and viewing activities in the sky and outer space but also we are losing the wonderful dark sky view with stars and other space objects that we used to enjoy. Many young people growing up in the city may not have the opportunity to experience this awesome scene if we continue to direct more light into the sky.

Health implications:

Disability glare, eye strain, loss of vision, and stress that people get from glare and spillovers are worth mentioning. Our eyes naturally adjust during day and night so we can see things properly. Too much light can harm our eyes and also harm the hormones (such as melatonin) that do this job.

Wildlife:

Many insects, birds, mammals, and reptiles are photoperiodic. Examples include sea turtles. Many aspects of their physiology and behavior are influenced by day–night or circadian rhythms.

This means their eating, mating, growth and development, movement, and other activities are about the balance of day and night.

Artificial lights, even in small amounts can distort their natural operations and cycle. Thousands of deer and animals are killed on the roads by vehicles in the evenings, because the glare of these cars blind them, and are unable to run off the streets before they are knocked down.