I believe nickel became popular because cartridges in leather belt loops were getting enough verdigris they would not chamber or had to be worked out of dumo pouches with tools. Hopefully no one is keeping cartridges in leather for long periods.
My nickel cases are mainly 30 wadcutter brass, though I did end up with 50 280 Remington nickel cases.
This is my understanding as well. Nickel cases for defense ammo isn't so prone to "going green" when carried at length. It has nothing to do with ease of extraction as mentioned above.
In days past, I used some Federal nickle plated rifle cases. Ostensibly, these were match grade cases and available only as components. I used them for .308 Win, .222 Rem and 6x47 Rem. Perhaps I should say "match" because I saw no significant benefit with them over others'. From what I can tell, they were ordinary, but plated, cases. Probably done for the bling factor. If you didn't shoot well, then at least you could look good!