>tfw this thread has actual discussion value

Why are mirrors real if we haven't even explained how magnets work?

English is a dumb language.

[spoiler]ME. is Middle English, the language of England between about 1100 and 1500 A.D. AS. is Anglo-Saxon, the language of the Saxon tribes that invaded England in the 5th and 6th centuries - from about 600 A.D. OS. is Old Saxon, the language of the original Saxon tribes of northwest Germany between the Rhine and the Elbe rivers.[/spoiler] forty: ME. forti, fourti, fowerti, from AS. feowertig; akin to OS. fiwartig, fiartig four: ME. four, fower, feower, from AS. feower; akin to OS. fiwar Four and forty were different words starting a long time ago, but were spelled with the same beginning in Old Saxon, Anglo-Saxon and part of Middle English. Somewhere along the way during the Middle English era the simpler spelling of forty took hold and has continued ever since.

Lazy English you so silly

There is no clear cut reason, just the bastardisation of several Germanic languages combined with the inconsistent spellings that are pretty common in English.

To shorten it.

I assume it's the same reason why any linguistic shortcuts are taken and why the American dialect exists: ease of use. The word 'for' already exists, so maybe that's why 'four' isn't contracted.