Scope creep mainly occurs when the interference comes from upper management. They see that a product is capable of A and B and then they ask if C is possible and push for it.
I think that a better way of preventing scope creep is possibly to turn the new ideas into their own projects, instead of just adding them onto the first ones. However, one large drawback to that is that it would cost much more money.
Although it’s impossible to completely get rid of scope creep (because ideas come when they come), it can be lessened by realizing that communication must be free and immediate from the beginning of the project.