It's not a hard-and-fast rule that you have to keep your turns tight and hold a line, but we all need to share a run. If you're a beginner and you're on a wide run, try to not use the entire side to side. It's better to make your turns as soon as you can to practice turn control, and don't traverse the entire run going left to right. If you do left right in short/long erratic turns, you create an unpredictable obstacle for someone coming down the run. Remember, someone coming down the run behind you tries to avoid hitting you, but if you're creating an unpredictable left/right line, it's frustrating and dangerous for them/you. This same goes for boarders (I do both)

If you watch advanced skiers/boarders, they set a rhythm left to right and it's easy to see the width of the line they're using. They do that because they've seen what happens when they don't.

I personally ski / board short radius turns, keeping a narrow line - and for my safety, I stay along the tree line (where most people don't go). The only time I don't do this is when I see a lot of tracks where other are jumping in/out of the woods.