Doesn't this depend on the stylistic environment of the text? Personally, I'd consider it alright given that the sender and the receiver are in a casual relationship. It only makes one seem uneducated if they are using it in a more formal, or perhaps a public context.
"You slip into a suit for an interview and you dress your language up, too. You can wear what you like linguistically or sartorially when you're at home or with friends, but most people accept the need to smarten up under some circumstances." - Stephen Fry, 5:00.
It made a lot of sense back when you had to type texts by pushing the same buttons multiple times. Now that smart phones have swipe to type and autocorrect, it is not a good excuse.
Nah it didn't even make sense back then. I could type full sentences with T9 easily, to the point that I wouldn't even need to look at the phone except to double check what I wrote before sending a text.