Why is someone who attends something called an attendee?

Shouldn't he or she be the attender, that is, the "one who attends", not as the word attendee seems to imply, that the person is the "one who gets attended"?

The definition does not seem to solve the problem:

attendee (plural attendees)

A person who is attended.

A person who attends (a function).

http://en.wiktionary.org/wiki/attendee

OK, so what's with our language: are the rules consistenly applied, or do just make up words? Like, the plural of "mouse" was always "mice", until, of course, the mouse became part of the computer, now it appears as if the plural can be either "mice" or "mouses". But if I has said, "The mouses are in the houses" a while back, well, what do you think?

mouse (plural mice)

Any small rodent of the genus Mus (informal) A member of the many small rodent and marsupial species resembling such a rodent. A quiet or shy person. (computing) (plural mice or, rarely, mouses) An input device that is moved over a pad or other flat surface to produce a corresponding movement of a pointer on a graphical display. (boxing) hematoma

http://en.wiktionary.org/wiki/mouse

Oh, just a couple more, while we're at it. Why do we always say, "The thing is, is that ..."? I even heard President Obama say that in a speech.

And why on earth do reporters always say "the alleged suspect"? Isn't that redundant? I mean, either the person is the suspect or not, right? Saying "alleged suspect" seems to question whether or not the person is considered a suspect or not.

Signed: Confusee