Everything we have now is better quality. Cameras and video cameras (including mobile phones) have more megapixels which = more space and we love to have the best possible quality if we can. Movies are better quality after going from DVD to bluray. People want to store lossless music such as FLAC instead of the lower quality MP3. People are also becoming more aware of backups and raid.
Luckily hard drives have got bigger and in general cost less per GB as time goes by
I'm also guilty of not cleaning up old computers or backups, so have a number of messy home directories backup up from as long as 15 years ago, as well as some very old virtual machines I should actually delete. There may be a time I can't find something and want to fire them up to see if it's on them though :p