The chain you did not want to start
The friendly email becomes a thread. Someone replies, their partner is a question mark, a cousin forwards it and adds a friend, a colleague answers from an old address, and a week later you are scrolling a chain to work out a headcount. The invitation was easy; managing the answers is the part nobody plans for.
A party invitation email that leads to a page avoids the scroll. The email itself stays short, one warm line and a link, because all the detail and the reply now live on the page it opens. A guest reads the plan and taps to confirm, and that confirmation lands against their name on your list instead of replying-all into the thread.