They don't count miss-tackles. Maybe they should. Same reason as negative rushing yards. Failing to do ones' job should count against them.
Failing to do ones' job does count against them. Do it often enough, and you don't have a job.
You have been harping on this subject since before the season started. When some lame sux fan stated that Keek falls on piles down field and still gets so much credit for all the tackles he gets.
Considering all the over the top, around the bend thinkers we have here on the Huddlez. And you cannot get even 1 of them to agree with you about your tackles for loss theory. That should tell you all you need to know about your thinking process.
Everyone wants to revolutionize the game. Take it from me. This ain't one of those times.