Seating on short railway journeys in now considered to be at a premium, with standee space very important- just look at the trains now running on Thameslink - so not many seats. TBH those who can probably prefer to stand over their luggage on this type of journey ( some may sit on it!) and seating will be intended for those who can't stand.
This is a big leap forward for LTN though and something it should have had 30 years ago.