Why isn't 11 pronounced onety one?

I know your question is asked tongue-in-cheek so forgive me for answering in a factual manner, I just thought this was interesting:

"Eleven in Old English is endleofan, and related forms in the various Germanic languages point back to an original Germanic *ainlif, “eleven.” *Ainlif is composed of *ain–, “one,” the same as our one, and the suffix *–lif from the Germanic root *lib–, “to adhere, remain, remain left over.” Thus, eleven is literally “one-left” (over, that is, past ten), and twelve is “two-left” (over past ten)."

More here:
http://www.bartleby.com/61/62/E0086200.html

Because we would be forced to pronounce twelve as onety-two, thirteen as onety-three...

Numbers are a product of the linguistic heritage they come from. In English, as a germanic language, the numbers 11 and 12 just happened to be "one more" "two more" than 10. (as Barcaluv pointed out).
In other language groups related to Germanic, similar rules operate eg Italic: undici, dodici (Italian) onze douze (French)once doce (Spanish), all derive from one-ten and two-ten in Latin.
If you go to languages much further away from European ones, however, the patterns are quite different
In Indonesian there are clear numbers for 1-9, but the number 10 is actually 1-(unit of 10). Eleven, however, is 1-(unit of teen) and twelve 2-(unit of teen)

Dunno.. it seems to be like that in most Nordic languages
Elf
Eleven
Elleve
No idea why though, may be because it's such a small number that there's been a word for it even before we began inventing the more structured words for numbers (twentyone, twentytwo etc)

If it were to be anything else, it would be "one-teen" and twelve would be "two-teen".

I think because the dozen is such a useful quantity, people carried on giving the numbers unique names up to this value. But once you stop using unique names, which you have to do sooner or later, our possession of ten fingers makes us prefer a ten-based system not a twelve-based system.

It wouldn't be proper ;)

Hmm.
Because if it was, it wouldn't be as entertaining to hear the guy in Spinal Tap say "eleven"

I thought it interesting when Bilbo Baggins turned eleventy one years old. LOL

For the same reason that 25 isn't pronounced "two-ty five." :o)

Actually, "eleven" and "twelve" were small enough numbers for early people to be able to comprehend, so they had their own names, along with "dozen" and so on.

Larger numbers fell into the "more" category, and so have the [tens] + [units] titles that you refer to, like thiry-nine and seventy-one.

Because that just sonds akward.

ROTF!! I gave you points for making me LMAO!! Sorry, but I really don't know why. I myself have wondered why it isn't called eleventeen. But onety-one sounds pretty good to me.

Perhaps because it would cause mass confusion between the pronunciations of twenty and onety? Or even that 10 is not onety on its own? Personally, I think who ever named the numbers starting getting lazy with the prefixes after they hit the 20 mark... Can't blame them, seeing as numbers go on forever and all...

i dont know but i think 116 should be said like elevendysix.

Because it sounds crazy!!!

You can pronounce it as onety one, but then only you would know what you mean lol (-:

Because eleven is derived from 'anelif' meaning 'one left'.

I think it should....it would be "betterer"