I wouldn't consider this evolving, nor degradation. Rather, it's simply changing or adding what's used for certain words (no matter how much someone dislikes the addition), like how "thou" became "you". However, there certainly is some kind of devolving going on if someone actually has to use "sup" in daily conversation instead of even "What's up?" or "How're you?"
On the topic of swearing, I do believe it to be useful such as in the case of tolerating pain, making exaggerations or denoting severity, but it's definitely not necessary; and many people do swear "too much," in the sense that it becomes a core part of their vocabulary.