Michael Crichton's foreword to the Audiobook version of Jurassic Park specifically addresses this point. The island is intended to be a theme park (e.g. complete with rides and attractions), not just a zoological garden for animals.
"I wrote a screenplay about cloning a pterodactyl from fossil DNA in
1983, but the story wasn’t convincing. I worked on it for several
years since, trying to make it more credible. Finally I decided on a
theme park setting, and wrote a novel from the point of view of a
young boy who was present when the dinosaurs escaped. I then sent the
book to the usual people who read my first drafts."
In the source novel, the character John Hammond gives us an insight into his own thinking on the subject:
“Well, Donald,” Hammond said, “to explain that, you have to go back to
the initial concept of the resort. The concept of the most advanced
amusement park in the world, combining the latest electronic and
As does John Arnold, the park's chief engineer:
“None of the rides are running yet,” Arnold was saying. “We have the jungle River Ride, where the boats follow tracks underwater, and we have the Aviary Lodge Ride, but none of it's operational yet. The park'll open with the basic dinosaur tour - the one that you're about to take in a few minutes. The other rides will come on line six, twelve months after that.”
“Wait a minute,” Grant said. “You're going to have rides? Like an amusement park?”
Arnold said, “This is a zoological park. We have tours of different areas, and we call them rides. That's all.”
Grant frowned. Again he felt troubled. He didn't like the idea of dinosaurs being used for an amusement park.