There are several reasons why you might want to transfer videotapes to DVD or USB:
Tapes rely on good, dry storage and good quality tape. The more you play them the more likely you are to notice white flecks in the picture. This is the tape breaking down.
I have noticed that the older the tape the more reliable they seem. This may be due to better production processes in the early days and cutting corners to make the tapes cheaper later on. I remember paying about £12 a tape when I first bought a video recorder.
Another problem is the deterioration of the video recorder. Older machines have rubber belts which perish over time. If you try to play your tape in a machine with a broken belts it will almost certainly get mangled!
So whatever type of tape you have, whether its a full size VHS tape or one of the tapes from your camcorder it would be a good idea to get them transferred as soon as possible if you want to save those cherished recordings.