wtf, so we thought dinosaurs didn't have feathers for all this time, now that we think they do we find proof like a year later
It's been a strong theory for ages, long before Jurassic Park 1 even.
Just to reiterate the others, it was actually right around the production of Jurassic Park that the feathers theories were being brought about. I think it was too far into production but more than anything it was too far removed from the public's general perception and understanding of dinosaurs for them to change the portrayal.
Nah it wasn't 'too far into production', they knew about it way before they started on the movie. Spielberg talked about this a lot - about how they wanted to include as much real-looking elements into the animal's behavior, movements and sounds, but not necessarily sticking close to reality. Movie magic/rules trumped reality for him. See also: basically switching the Dilo and Raptor sizes because it seemed cooler for their respective action sequences. They never claimed it was all supposed to be as close to 'real' dinosaurs as possible, just real in the sense that, given the then-current leaps in technology, it seemed like it
could be real. Not doing the feathers was a creative choice, not a lack of knowledge.
That's why I could never get angry over them not doing feathers in Jurassic World. The original also played it very fast and loose with reality, and the established look for creatures like the T-Rex and Raptors are iconic at this point. Makes complete sense to me (within that universe) to stick to that, and the idea that they're altering the creatures to fit the audience's expectation/their coolness factor is a part of the original novel as well (as well as, very lightly, Jurassic World). Walking with Dinosaurs was always the place to learn about how they actually lived back in the day - that's the place for the feather discussion, not a theme park popcorn flick.