[Cthulhu_]

One reason I can think of: Egos. "Why should this guy get credit after having left the project years ago while I still work full-time on it and all I get is an entry in a generated contributors file? No fair!"

I mean the OP (Gabriel) hints at wanting to use it in his CV (proverbially); wouldn't anyone that made a significant contribution? Then of course, how would you define significant?

It's a can of worms and one of the ways around it is to reduce all contributors to "you are not special" status.

[JangoSteve]

To be fair though, that's kind of life. The originators of any given thing always get remembered as the originators, despite how long they worked on it compared to anyone else since. This isn't just code. I mean, 30 years from now, George Lucas will still be remembered as the creator of Star Wars, even though by then I'm sure the writers at Disney will have produced 20x more stories around it, and Stan Lee/Jack Kirby will still be remembered as the creators of the characters others have already built upon and adapted since then. Even the USA has had far more people build and mold the country into what it is since the founding fathers. It's just one of the hallmarks of our society I think to romanticize and glorify the original creators of works.

I think reducing everyone to "you are not special" status is a pretty weak solution that probably wrongs more people than it rights. And I think egos are a pretty weak reason to do it.