Charlotte Hertzberg: Because the meeting organizer might have invited a lot of people to the meeting and their inbox would be completely overflowing if each of them are sending a response.

Unfortunately, as R.S. notes, you are not listed as attending the meeting (in the 'Registration' tab) if you accept the invite without sending a response. Otherwise, the meeting organizer could check back after e.g. a week and see the number of attendees without having their inbox overflowed with responses.

100% agree. I want to confirm that I will attend but not send a bunch of useless email.

You don't have to worry about the recipients inbox. There are options to handle the invitation responses automatically without getting a single email in your inbox. Except the ones that come with some written message attached.
File -> Options -> Mail -> Tracking