Why do people get prescribed modafinil?

https://www.smartfinil.net/product/modvigil-200/

Modafinil is used to treat excessive daytime sleepiness brought on by shift-work sleep disorder, narcolepsy, or obstructive sleep apnea. It enhances focus, alertness, and general daytime functioning. Many patients who use Modvigil 200 report greater productivity and reduced weariness.