it's easier to do lots of things on aged domains.
for example, if you register a domain today you CAN'T began building 1000s of links to it because it will raise flags in google's eyes.
but if your domain is 8 years old and you began building links quickly, google won't think to much of it because the sites been around for so many years.
lots of other benefits. easier to get ranked, not in the sandbox, better link building techniques, etc