A lot of these things were well-known clichés already before LLMs, used by people who wanted to sound sophisticated but weren't articulate or didn't have anything to say. That's why LLMs sound like that.
The interesting thing is that LLMs sound kind of like LinkedIn Growth Hackers even if you don't explicitly tell them to do that, unless you instead tell them to sound like something else. (And even then, there are still similarities.)