But I already use Calendar/Contacts/Facebook. Why Dearly?

Three places already hold the date. None of them help you plan around it.

You don't have to start over. Dearly can import dates from Contacts or your calendar in minutes. Facebook import is not available.

Calendar

Does well

Calendars are dependable. Put the date in once, and it's there every year without fail.

Falls short

Calendars are not purpose-built for relationship care. Without intelligent lead times or thoughtful reminders, a birthday sits in the same box as a dentist appointment with basic, unreliable notifications.

Contacts

Does well

Contacts keep the date right where it belongs: next to the person, not buried in a calendar view.

Falls short

Contacts can now send basic notifications, but there is still no list view of upcoming dates and reminders are not actionable. The date remains static inside a contact card rather than helping you plan ahead.

Facebook

Does well

Facebook still surfaces birthdays in a feed, and it's the only one of the three with any real list view of what's coming up.

Falls short

Fewer people use it regularly, especially younger generations. The birthday feed is noise rather than signal, and notifications get lost in social clutter.

None of that makes them bad tools. It just means important dates need a place built around the people they belong to.