I hope I don't kill this for people abusing this.
Every once in a while, myself or my mates will 'pretend' it is their birthday when we make a restaurant booking.
That way, we get top tier customers service, or freebies like cake or dessert or snacks. We have gotten multiple free shots taken with the owner.
Sometimes the waiters come sing happy birthday, or you can request for them to sing in their foreign language like Japanese for that free Japanese experience without going Japan.
All around happy vibes.
It's also quick way to also test the level of service from a restaurant and whether they go above and beyond to deserve your fat tip.
I know it's not Australian customs to tip, but these waiters/bartenders are the ones worth tipping. Always tip them.
Edit: Included hotels, anniversaries, graduation, celebrations and any other 'special occasions'
Happy Birthday!. :+)