This is the answer. Mail & Calendar together in one app go back into the days before we had multitasking OS. So it does make sense to include both functionalities into one application, because you couldn’t easily switch to your calendar “app” like you can today or even share the appointment easily. And since this is going back for decades, this is also baked into users workflows. So if you don’t have a calendar, many users will not use your mail software. Calendars are quick & easy to implement and don’t need much maintenance, so there is little reason to not integrate them
Calendar invites mostly come via email so it’s easier to schedule from inside the email client, for my experience
This is the answer. Mail & Calendar together in one app go back into the days before we had multitasking OS. So it does make sense to include both functionalities into one application, because you couldn’t easily switch to your calendar “app” like you can today or even share the appointment easily. And since this is going back for decades, this is also baked into users workflows. So if you don’t have a calendar, many users will not use your mail software. Calendars are quick & easy to implement and don’t need much maintenance, so there is little reason to not integrate them