Hi I've never had IEMs before. I've had a pair of $30 Sony earbuds with soft paddin(?) that block out ambient noise very well. The thing is I could hear all the vibrations from the cable when I touch them. Not to mention all the crunch sound when eating snacks and stuff. If you don't know what I'm talking about, do this: Plug your index fingers into your ear and then try rubbing your index fingers with your thumbs. The sound is really loud and very annoying.
Are IEMs the same?
Sorry for my bad english. It is my second language.
What you're referring to is "microphonics" and most IEMs suffer from them to some degree. Shirt clips, and over-the-ear wearing style can help mitigate that. And some cables are more microphonic than others.