Because your DVD player doesn't play AVI files and you are burning them to the disc the wrong way. You are burning the disc as a data disc, you need to burn it as a DVD video disc. That way it transcodes the video into the proper mpeg2 format and put the files in the proper format on the DVD.
The information on Computing.Net is the opinions of its users. Such
opinions may not be accurate and they are to be used at your own risk.
Computing.Net cannot verify the validity of the statements made on this
site. Computing.Net and Compnet Ventures, LLC hereby disclaim all responsibility
and liability for the content of Computing.Net and its accuracy.