Some people just can’t be bothered to program efficiently. Probably because they don’t suffer from it, while using their stuff on gigahertz-class machines; I invite them to check their work on my old server, just look at the time WordPress needs to render this page, or here (and this is just the index page!)
Compare that with the speed on other parts of this site, even the heavy (compared to WordPress) database stuff in my personal account manager is much faster.
Fortunately, the upgrade of this server will be done; it’ll be replaced with an UltraSparc 5 in march.
Edit 1: As Yann points out, it’s going to be an Ultra 1, not 5.