This is the manner by which your Solar System was located, not by us, but by others. If the probe returns with data that indicates an environment that would be poisonous or quickly fatal, we do not, understandably, explore that part of the Universe. Travel in light form, during higher densities, does not carry those risks. Different sections of the Universe have different compositions. By this we mean the elements are found in different proportions and the resultant chemical reactions that ensue therefore have different characteristics.
Some worlds have silicon based life.
Some suns emit radiation that is poisonous to us and would be to you also. Those environments contain severe dangers, as silicon based microbes are ones your immune system could not begin to muster a defense against. An analogy we could use is the soil across a terrain. One place is acidic and is covered with moss, another has soil that compacts into rock-like hardness, discouraging probing roots. The variables are many, and any horticulturist will tell you that a wildflower taken from one location could not be expected to grow in another.