The chat carries the news; the page has to carry the details
Nobody waits for printed invitations any more. The engagement lands in the family group, then the work group, then the cousins' chat, and inside an hour half your guest list knows the date. That part is fine. The second half is where the weekend starts going wrong.
Every forward of a typed-out message loses something. The ceremony venue survives the trip, the reception address gets dropped, somebody rewrites the start time from memory, and by the Thursday before the wedding you are counting heads from a notebook.
A wedding invitation page in WhatsApp settles it by being the thing that gets forwarded instead of your typing. One link, one version of the day, and a reply button under it, so every yes, every no and every plus-one arrives in the same list you can actually read.