Because the word glass is a proxilimintator to the word plastic and cup, therefore making people get the two mixed up.
JK, How should I know?
If my pants are on backwards, then does my pants think that I'm on backwards?
To tell you the truth,
I got my Wii when it first came out for Christmas and played it for like 2 months.
Then it got old.
I don't think I played it since and its just gathering dust.
I'm an Xbox kid.