Why do the gas giants in the Solar System have comparatively large orbits compared to the inner planets?

When the solar system formed, there was an accretion disc, spinning around the newborn Sun.

The Sun was emitting radiations, which pushed the lighter materials of the accretion disk (gases) further away, and kept the heavier materials (rocks) much closer. This is why gas giants are almost always further away than rocky planets. Almost.

In the case of "hot Jupiters", astronomers think that they simply spiraled their way to their star, "eating" smaller planets on their way. It doesn't happen in our solar system because Saturn holds Jupiter back.

Exact source nowhere to be found on the internet, but everything I wrote here comes from a very interesting movie I watched in "La Cité de L'Espace" (Space City) in Toulouse, France. It is a famous exposition / museum about astronomy and space exploration.