About pools outside the combat, Are they used? Options

[Traks]

So, I admit that I am not too knowledgeable of Shadowrun rules.
Although I am doing my best to learn them :)
Now, a question. Do pools get used outside the combat, on mundane tasks?
Or you just use skill in question (with complementary skills, if applicable)?

If second, another question arises:
Then why you should learn Negotiations if you can use Charisma?
You can surely use those points elsewhere and default to Charisma everywhere in social skills. It will have higher difficulty rating (+4?) but generally it is worth it.
And if you have no negotiations but have psychology, can you use complementary skills to help it? (I remember reading somewhere that answer is NO).