Plants that can use more light generally require more energy to live. Thus, plants living on the forest floor in low light (because trees above them are providing shade) don't need as much energy, but they also don't use as much. Plants that grow in the open sun often can use more energy, but those plants wouldn't survive if they were in the shade all of the time.

Additionally, too much light increases temperature and with it evaporation. Plants that live in dry climates have adaptations to reflect away excess light to avoid getting too hot and losing all of their water.