1. WordPress is very proud of its quick-setup process, and caching needs to be configured away from the defaults on a non-trivial number of systems.
2. Using caching makes your blog less dynamic. Things like "latest comments" don't update immediately across your site. Users who haven't explicitly installed caching don't necessarily understand why this isn't a bug.
So WordPress makes it really easy to install a caching plugin, and lets the tiny number of blogs that get enough traffic to need it install it themselves.
1. WordPress is very proud of its quick-setup process, and caching needs to be configured away from the defaults on a non-trivial number of systems.
2. Using caching makes your blog less dynamic. Things like "latest comments" don't update immediately across your site. Users who haven't explicitly installed caching don't necessarily understand why this isn't a bug.
So WordPress makes it really easy to install a caching plugin, and lets the tiny number of blogs that get enough traffic to need it install it themselves.