What could prevent a sentient species from going to space?

I am still puzzled by the original The Planet of the Apes movie from the 70's. How come that sentient species invented weapons, but was unable to develop powered flight, or spacecraft. Thus, the question is:

What could prevent a sentient race from going to space?

Assume an earth-like planet, and human-like species. This race should get through similar history build-up as humans, with one twist: They should not go to space.

What is most obvious factor to prevent them to go to space?

By "space" I mean not being able to pass first orbit, and never launching satellites. But otherwise, I would like to get this race to at least Earth 70s technology level.

This planet has all the resources needed to get to the space (basically think of alternate Earth)

posted almost 8 years ago

Pavel Janicek‭

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