Why Not Keep Mongoose Traveller 1st Edition Books?

I was asked about 1st edition Mongoose Traveller about a week ago. At a game store, someone brought up the green titled books, and if I was going to keep mine or not.

I figured they were talking about the new 2nd edition being released, and that maybe they were thinking the 1st edition books were not compatible. I didn't have much time to answer, because of some game events starting up. I just remember saying that I planned on keeping the 1st edition books because of their advanced character generation rules.

As I was heading to my car, I was thinking about the different books. One of them was Cybernetics. And I had forgotten why that book was yellow instead of green titled. I think I was driving to Krispy Kreme, still thinking about it.

I just now thought about that question again. And looking at my Traveller bookshelves here, I'm seeing that the book is indeed one of the yellow ones. Which means the rules are not strictly for the Imperium setting. They're more generic in their use.

So I started looking at the other yellow titled books I have. I'll be keeping those as well, because of the generic-ness of them.