When my daughter was about 5 we were on public transit and a bunch of teens were talking near us. Every second or third word was 'fuck' or 'shit'. My daughter asked why they talk that way. I told her it was because they didn't know enough words to say what they meant.
15 years later, she speaks two languages fluently and 2 more at about middle school level. She swears a little, but she knows how to say what she means.