CalDav Calendar support - No Invitees Function

On my iPhone Xs iOS 16.3 I added a CalDav Calendar from my mail service provider (Bluehost). The CalDav calendar added just fine and am able create events. However, when I create an event with the CalDav Calendar the “Invitees” feature disappears. 

I added the same CalDav Calendar to my MacBook iCal computer. The Invitees function shows up but does not send notification to invitees.   

When I switch to an iCloud account, the invitees and invites works fine - but invites come from my iCloud email.  

Why is the calendar Invitee function not working with a CalDav account?