One message, two jobs
A graduation announcement gets typed in a rush between congratulations: the date of the ceremony, maybe a photo, and a trailing sentence about lunch next month that nobody can find again later. The trouble is that the news and the party are two different questions guests have, weeks apart, and a single chat message answers neither twice.
A page handles both at once. Announce now with the ceremony details, and the same link carries the celebration as plans firm up. Relatives who open it in April and friends who open it in June see the same current truth, and the people who mean to come simply tap the reply button while they are there.