Here's a trivia, Any idea why?

No counting is necessary. You just have to realize that the words one through nine, the suffix teen, the words twenty through ninety and hundred do not have an "A" and it becomes obvious. It just works out that way in English and is not true for some other languages such as Spanish. So it just depends on the roots of the particular words for the language you are considering.

i've known this trivia a long time ago! a friend sent it to me via a text message. it really did make me counted but not from 1 to 999. LOL its amazing when i realized it was true. was that a coincidence or something... ^__^

That is pretty interesting and I had no idea that was true. Yep, I did some counting just to make sure! Right now I can't think of a single trivia fact to come back with! Thanks for sharing.