WordPress, by default, does a form of "Object Caching" but its lifetime is only a single page load. Let me explain you what exactly is the
Object Cache in WordPress, because I see that you are not familiar with this matter:
Options (extracted from database table
wp_options) are actually a really good example of this. The summary:
- A page starts
- All options are loaded with a simple
SELECT option_name, option_value from $wpdb->options statement
- Subsequent requests for those options (eg a call to
get_option never hit the database because they are stored with the WP cache API.
Options always "live" in the database and are always persisted there -- that's their "canonical" source. That said, options are loaded into the object cache so when you request an option there's a 99% chance that request will never hit the database.
So to speak, Easy cache plugin make very few requests to the database to get his options and they are all cached, by default by WordPress, so the Object caching is enabled by default (because actually this has nothing to do with the plugin, but with the WordPress system).
Transients are a bit different, but the Easy cache plugin does not use them.