There is one reason to get the JTAS.
Issue #9 -- WAR
I still remember as an impressionable youth when that issue came out talking about the start of The Fifth Frontier War.
I swear I felt like I was on a desert island and stumbled upon a "JAPS BOMB PEARL" headline in mid-1943.
If I actually had any "Fellow Travellers" I would have run to them screaming "HOLY 5417! The Joes are coming! And I'm stuck on this lost, Tech 8, balkanized rock!". To me it was a really shocking issue.
Most games had, you know, scenarios, adventures, equipment, what not and what have you. You could give or take whatever. Traveller gets all that and Interstellar War. It was truly an OMG moment.
Obviously it won't have the same effect today, but that's the kind things that made JTAS important. It helped detail the growing universe of the evolving 3rd Imperium.