It's for sure a culture thing I agree, but also on the Canadian side where if you're a decently high pick you typically sign because that's what everyone's done before you (thus creating the culture). I agree with others that guys like Martone, Misa, etc don't need more years in junior and should absolutely take their game to the NCAA.
I think this notion will slowly change as people realize it's not a slight to not sign in your draft +1 or 2. A spot will be there for them when they're ready. All it takes is the first couple kids to do it and people will realize it's literally no big deal to not sign with the NHL team right away. As you know, this hasn't hurt Americans that've done this for years, or even guys like Hage, Boisvert, and Wood that chose the NCAA route. Not signing right after you're drafted will be a non factor in a few years.