Not Giving Credit In Games

Well you see, when they say software engineers, they lie a bit.
An engineer is designing the solution, he is the architect. A programmer does that as well, but on the other hand a programmer is also the hard labor worker.

Programming requiring a lot of "dirty work" makes programmers replaceable.
Not only that, but writing readable and maintainable code is not necessary to implement features.

Companies want their programmers to THINK they have good conditions, they give them just a bit above average to make them think they have a really good job, but they also keep them under constant stress.

Most people in the hi tech replace work places every 2 or so years. There is no job security in software engineering.

The shareholders want their workers to be happy as long as it serves their purpose, they could lay off and rehire people for the tinniest reasons.

That being said, I was told by some guy who works at a big AAA studio that they have a very defined rules for that, and that every person who stays more than 3 months get credited.
Not only that, he said that if you don't get credit it's probably because someone forgot to put you in the list and you didn't tell them to put you there.
i.e. it's more a human error rather than malicious or a policy.