[JoeUserName]

The answer lies in your question. Text messaging is not thread capable. There's no subject line, category, importance flag, or other distinguishing field to make a thread to tie the messages together. The ability to even have a thread, would be an important part of any "threaded messaging" functionality I would think.

Threaded messaging is the ability to tie messages together to form a conversation which is distinguished primarily by a subject line or other information fields that when tied together would make....a thread. This is commonly done in email, BB's, message boards, and other (relatively) heavier means of text communication.

Grouping messages by sender does not constitute a thread, that's called....grouping messages together by sender, which makes it extremely difficult to read SMS text messages if they cannot be sorted in any other method. Therefore removing it's top appeal to even use as a means of communication. Which is to send quick, lightweight (minimal fields, so no subject, etc), short text messages to another user. Attempting to turn it into email or instant messaging client, is just...stupid, and ruins the primary reason to even use it. Email already exists, so does instant messaging, and other text forms of THREADED communication. SMS, by definition, cannot be threaded.