Idea: Add-To-Outlook calender for contact birthdays.
Yes, you can add birthdays to people in Outlook, and yes Outlook creates an event for it.
But that is exactly want you don't want.
On Android and iOS contact birthdays are shown from the contacts birthdays.
So Outlook making another appointment for it will give you 2 items about a birthday, which isn;t needed.
To solve the issue with Outlook, we could enter the birthday on web, phone or tablet and maybe we can gather them as a Add To Outlook calender to show the dates as a birthday calender so we still can see our contact birthdays in Outlook.