Why is illiteracy so "cool" to our teenagers?

If you're referring to slang words then, its all about trying to get the audience attention. Usually these kinds of teenagers face lots of problems while giving their examination. They would usually use slang, or short words.. that's how the society already is nowadays..

Unfortunately it has always been like this, even in my school years using slang was always 'cooler' than using the actual spelling of the word. Hopefully just like I did they will grow out of it, but yeah it annoys me too because it makes them look so low class and uneducated.

do you mean when they write like this: tryiN' t0 f0rgEt s0mwUn yEw l0ve is lYk tryiN' t0 rEmEmbA s0mwUn yEw nEvA mEt!

if yes, they just want to have more attention from people...to look more interesting...like you said: cool..
it's very annoying to read when they write like this...

Perhaps you could give us more information about the problem because some people (myself included) may not understand the question well. Please use the edit button on your question to make amendments. I'll change my answer once you make your question more clear.