You may leverage the reach and impact of your original and valuable new content by hosting it in an old website instead of setting up an ad-hoc site for it. In SEO terms, old sites are 5 years old or over (1). Google disproportionately values content hosted on old sites. This translates into higher ranking and greater exposure of content.
Google’s ranking algorithms evolved to value trust over popularity. Trust is only obtained in the long term. Popularity is abused by web spammers by artificially inflating the number of links that their sites obtain. On the other side, new content may rank high thanks to QDF or Query Deserves Freshness but it only operates in the short term.
Buying a new domain and setting up a new site is probably not the most efficient way to expose your content to the maximum audience via Google. Does your organization own and operate sites that are no longer in use? Trust is more often than not wasted by not re-using old sites and starting from scratch on new, unknown sites than only reach their potential to rank higher after many months and years.
Old sites get usually neglected after a change in the business model they were setup to sustain, a drop in passive revenues such as Adsense or a shift in the priorities and motivations of their stakeholders.
In many regards Google, perhaps unintentionally, keeps reinforcing a gerontocracy of old sites that lost the high rankings of their best days long ago but who plague the deeper results pages for many competitive queries. New sites, no matter how valuable and disruptive their market proposition, struggle for too long to elbow out those old patriarchs that have outdated content and whose usability and design are lacking.
Of course this phenomenon did not escape the attention of search experts in the early years of SEO. Buying old sites to harness their trust and links is an old practice that Google still fights to eradicate. That makes the business of acquiring old domains and sites a risky one.
There is a whole new expertise of SEO consisting in
1. maintaining your portfolio of sites with new content and links
2. re-engineering broken and links from third parties to retain and grow the trust that those sites, should they be needed in future.
Old sites retain their trust if properly managed over time. Hosting new content on old sites is frequently a safer, faster and more efficient way of promoting it on Google and other traffic sources on Internet.
(1) a new site is up to 6 months old, a young site is between 6 months and 2 years old, a maturing one between 2 and 5 five years and old sites are older than 5 years