Neither. It's because it's extremely difficult to keep large animals confined indefinitely through all circumstances. Ask any farmer with livestock. The bigger they are, the more capable they are of ignoring whatever fencing/obstacles you put in the way.

Zoos keep Rhinos. They manage without the kind of budget that a resurrected dinosaur would afford. They also keep elephants, 800lb gorillas, chimps, ostriches, all kinds of powerful and intelligent beasts capable of reproduction. They sometimes escape, but it's the exception, and killing the animal(s) is always a last-ditch option.

That last point is another place where I expect a huge fiction-reality gap. If I pay to watch a movie about a dinosaur getting loose, I want to see it shrug off bunker-busting missiles from fighter jets, with big fireball explosions and people jumping in the air and the hero magically surviving. I don't want to see a short, sad walk down to the city park where they try and fail for an hour to coax it back and ultimately decide that they have to shoot it with a slightly larger than average rifle. That's the boring and horrible but realistic scenario.

There's nothing wrong with the movie scene not being realistic, but there is something wrong with blindly assuming that the movie scene is realistic.

> They sometimes escape, but it's the exception

That's... kinda my point!

Zoos keep large animals in significantly smaller areas that are easier to control and maintain. I can see someone making "Jurassic Zoo" where you're keeping a few fairly docile dinosaurs in an area of a few acres. I don't have hard data but the territories in Jurassic Park look like they were measured in square miles.

If "escapes are rare and low-consequence" is your point, I'm happy to agree.

Re: enclosure size, that's because city land is expensive, not because the mathematics of chaos theory dictate that it is impossible to hold an animal in a large enclosure. Come on.

It's because the scriptwriters tried selling a script where nothing much happened, and didn't even get past the receptionist.

Nobody likes "Billy and the Clonosaurus".[0]

0: https://www.youtube.com/watch?v=wIUh-MHsQKU

Isn't it almost always that the safeguards in place are poor? Either poorly maintained or the caretakers don't care at all.

Jurassic Park is a great example of hard scifi in that the problems which happen all happen in believable ways.

It's still fiction and not an attempt to realistically estimate the rate at which problems would happen or the magnitude of those problems if they did. Look to zoos if you want a realistic point of comparison for the risk analysis -- but not if you want to watch a T-Rex chase kids in Jeeps.

Yep. I was actually thinking of zoos as a counterpoint to my post upthread. But the difference is that of scale: how do you allow a T-Rex or a herd of brachiosaurs the square miles they need for their territory and still keep them within that territory? You may as well just say, "let's not bother fencing them in and just use the ocean itself as the barrier."