The point of those LTS browsers is so that an employer doesn't have to watch for UI changes in their browser every 6 weeks, and then retrain all their staff when the browser moves things around or makes things look different.

Some of us are using browsers imposed upon us by $EMPLOYER, and may not be able to update of our own volition.

I think Firefox 24 is still supported for a few more weeks, as it is a "long term" release.