There were questions as to the usefulness of it. It was originally added as an aid to debugging in that each request would have a number so that when looking through request traces you could see a change of URL between requests. If it goes in the POST data it isn't much use for that, although you could still see it if you dug further.

The `tid` itself is only a number between 1 and 10 so the question of whether it was actually granular enough to be of use was raised too. I'm not overly concerned with it being dropped.