You don't have to use them. I'm not until recuring tasks and ways to email in tasks arrives.
I tend to split events and tasks. For me, a Drs appointment is an event, so it goes in the calendar. I look at my calendar multiple times a day and get a reminder 24 hours and 1 hour before an event starts.
Tasks are for things I must do like write a report, invoice a client, create a presentation etc.
You fit the tools into your workflow but it's fine if you don't use them.