Email template event – Not attending button

We had a discussion here with some colleagues about an e-mail invitation for an offline event. 99% of this is the plan:

1. Email list with firstname, lastname, email
2. Import mailing list into system 'XYZ'.
3. Generate a mailer template
4. Send the e-mail.

In the case of the invitation for an offline event, you can expect a call to action button, 'subscribe' which will lead to a website with the registration form, where more details are given.

Now the main question: Do you think it's a benefit of having a 'I am not attending' button in the e-mail template?

I said "No" because:

1. Your e-mail tool that sends the emails, probably measures whether the emails were openend or not.
2. People, who aren't attending the event, are not going to take the action to click the button 'I am not attending',... maybe 1%?
3. When you have 1 a mailing list, a number with who has openend or not the e-mail, you can perfectly have a view on the people who are not interested.

What is your opinion about asking a user to click for such action?

Thanks!