Low-pressure weather systems usually bring windy and stormy weather, it's considered "bad weather".
In a low-pressure system, the air is warmed up by the ground, raises in the air bringing humidity from the ground up in the sky. The air going up creates winds and clouds. That can lead to a cloudy sky, to winds and even precipitations. That's why it's usually considered "bad weather".
The opposite, the high-pressure systems, are usually associated to "good weather" with a clear sky and all.
