Interesting. I always thought this form of writing was to cut down on the number of words in an email, so that the reader can more easily skim for the overall message, while also reducing formality and increasing familiarity. I've even recently tried to start emulating this style for those reasons.
If you said text messaging then I would agree. That's the first thing that came to mind because traditionally everyone wants to save characters when texting resulting in ur, b, etc.
Actually, with texting, I find it harder to shorten words into misspellings like ur or b, because I end up fighting against my phone's autocorrect. Sure, once you use it a few times, your phone will learn to stop autocorrecting, but why bother? I don't understand why people still use "ur" when "your" is just as easy to type these days. SMS length isn't really an issue anymore either, with most smartphones automatically concatenating longer messages for the recipient.
That is true, with smartphones this has changed (or should have go away). The issue isn't really about concatenating--I had nokia phones with just a keypad that did that years ago--it's the fact that often you can keep a message short and only use 1 message with the shorter "words". This won't make a difference if you have an unlimited text plan but it still matters for some people.
