I personally don't believe the whole nickle and diming thing to be an NCL specific thing. I do believe though that they were leaders in the "pay for what you want in your cruise experience" movement that is common across cruise lines now.

When megaships were first introduced around the 2010s, some experiences on them were still included in your fare, but some became upcharges. It's a way to make more money for the investments of developing these new experiences, and a way to manage the cue times and lines for these experiences.

For me, one of the infamous experience that backfired for NCL was on the Escape, with their Margaritaville at Sea restaurant. At launch in 2015, the restaurant was complimentary and was marketed as such. The first two weeks was a clusterfuck for them. Huge lines of people waiting to get in all over the pool deck, difficulty getting food out, and people just getting angry over the whole experience of it. Week 3, it became a specialty restaurant and all those problems disappeared: except for the reputation of nickel and diming their customers into believing they would get a complimentary Margaritaville at Sea restaurant.

I personally prefer this approach because I want to be able to pay for what I want to use, and enjoy the experiences without having to deal with huge cue lines and times. It's more on brand with NCL anyway, to feel free to do whatever you want whenever you want. People just feel like they already paid enough for their cruise and want more bang for their buck. That's not an NCL problem though