If you are the person
chasing the replies.
The guest does not install anything. They open a link.
Weddings, engagements, receptions
Families split across cities, a venue that changed once, and an uncle who is still working from last week's message. One page holds the current details. Each guest still has their own reply, so the mehendi list and the reception list do not land in the same pile.
Birthdays and anniversaries
Useful when the guest list is small but the same questions keep arriving: what time, where to park, whether children are coming. A personal link is enough. Nobody has to join a group they will mute.
Housewarmings, poojas, and other ceremonies
These are often planned by one person and attended by people who do not all use the same apps. A normal link works on the phone they already have.
A poor fit
If you need ticketing, paid registration, or a floor plan, this is the wrong tool. InviteLink is the invitation and the reply list.