May it be a video player or a PC drive, DVD drives will fail in time due to wear and tear and the occasional paperclip your children slip into them. These drives are electro-mechanical, meaning they have both mechanical parts that move and wear out as well as micro-electronics that moves the head, reads data and translates it into a format that the computer or TV can use. Most DVD drives are digital so to get a video signal out, you’d need an analog to digital converter to do the translation from the 0′s and 1′s on the disk to the video needed for displaying it onto the screen.
Whenever they fail, they can sometimes be revived with some cleaning yet being precise devices, replacement may be the only option. As with any technological products may they be for your computer or digital video system, they are on the side of disposable gadgets meaning most failures means they have outlived their useful life.