The reason that all known solar systems have hot Jupiter’s is because that is all we can detect at the moment. A large massed planet close to its star not only tugs that star more than a less mass planet, it also orbit the star in a short time.

All plants tug at their star. The larger, more massive, the planet, the more apparent and larger the tug. The shorter the planet’s year the more apparent the stars wobble due to the planet’s tug.

I don’t think we have the means yet to detect an Earth type planet using this star wobble method. This doesn’t mean they are not out there or are less common than the hot Jupiter’s.

To simplify, the only reason hot Jupiter’s is all we are finding is because with out available tools, that is all we can find.