TTFB slow after installing plugin. Plugin blocks caching

Support forumCategory: BugsTTFB slow after installing plugin. Plugin blocks caching
michel_kieboom asked 3 years ago
I noticed my website was running slow on Time to first byte tests after using your plugin.
I've deactivated all plugins and tested them one by one. Conclusion: the Easy Appointments app causes this, there's a header:
$ curl -sIL scanit.nl | grep cache-control
cache-control: no-store, no-cache, must-revalidate

Why is this done and how can we avoid getting a slow overall website. It's fine if the plugin blocks caching for the page where the plugin is used, but not on the complete website!