Quite a few people still use 8 or 10 year old machines, single-core or slow dual-core with a few gigs of memory, smallish harddrive, and still running Windows XP.
When a machine from 2006 can comfortably play videos on Facebook, who _needs_ to upgrade?
The fastest machines I have in the home office are dual core, 4 gigs memory, 250 or 500 gig disk running Windows 7 and Xubuntu respectively. They both perform very well.
The oldest machine is a Dell laptop from 2002 with Windows XP for use as a print server. It is slow but functional. Was using Xubuntu which was much faster but my scanner didn't like Linux.
tldr; Unless you are into new games, you really don't need a new computer.