To be called an "engineer", you need to be registered and licensed by the state. It's a highly regulated title in the US. Software, computer, electrical, etc. in the IT field are no different. (See the PE section under NCEES's website.)

Now, I know what you're saying. Yes, you're right in that you can still work in the engineering field without PE. However, you would be working UNDER and SUPERVISED by a licensed PE, and you are NOT allowed to release drawings, projects, plans, etc.

You are also not allowed the name/title of engineer. Your hiring company cannot legally give you the title, and you cannot legally use the title in your resume, card, etc.