VHS
Over time video tapes degrade. . Each time a tape is idle for a long time and each time a tape is played the quality of that tape gets a little worse. VHS is a last century technology and at some point will be all but obsolete., It is highly recommended to convert VHS tapes to DVD as soon as possible. The advantages of converting to DVD include: an extended life of your memories, no quality degradation, much more convenient for watching and duplicating. Most people have determined that the small cost of transfering their VHS tapes to DVD is will worth the piece of mind they get, knowing their captured memories are more safe and secure and easier to watch.
Hi-8, Digital-8, MiniDV
The same applies to these types of tapes. They degrade easily, they are easily lost, they are hard to organize and if they are not transferred to DVD they can only be viewed using the device used to capture them. Many people take a lot of footage with their camcorder but end up with a lot of tapes in a shoe box. Capturing those tapes and burning them to DVD preserves the content, makes them viewable with a DVD player and makes it much easier to duplicate.