Over time, languages change.
If you've ever taken a Linguistics class, that's pretty much day one. Through Day 365. The problem is, naturally, that when changes occur, it's because the language is growing more complex and complicated, not simpler. Things start simple: pidgin languages are simple nouns, with a small spattering of verbs. No adjectives, no grammar, no adverbs, prepositions, etc. Then, as a pidgin becomes a creole, the language grows more complicated. Now we're talking about fully-developed verbs. A sense of syntax. Adjectives make an appearance. Then, after a generation or two, the creole is a full language. Grammar, adverbs, syntax: all are fully developed.
That being said ... "Text Speak" is not phonetic. "ur" is not pronounced like "your." It's pronounced like you've just received head trauma, and you are unable to think properly. How come no one else notices this?! Argh, it frustrates me.
Previous to, oh, the seventeenth century, spelling was not rigidly defined. If you read Chaucer, for example, you'll see the same word spelled in many different ways, often in the same sentence. At the time, it was a mark of literacy (believe it or not) to be capable of spelling the same word in multiple ways.
I'm actually a bit surprised no one has drawn this comparison: Newspeak! This is freakin' 1984. They're just trying to dumb things down. It starts with the minor concessions. Then, unneeded words are dropped out: how many words do we need to explain "red"? Then, the opposites are left off: why do we need "bad" when we can just say "not good"? But then, we lose the need for "not" since we have a perfectly good prefix: isn't "ungood" just as valid?
The complexity of the English language is what allows for self-expression. Explaining the different between vermilion, crimson, and scarlet is one of the great wonders that English provides us. If anything, I would maintain that English needs more words, more complexity, and more subtle connotations. It's what makes the language beautiful.
... I'll get off my morally indignant high horse now. Or my moralie indignent hi hors naow.