It many countries it actually is, if you call yourself an engineer professionally without a license you can be heavily fined. Canada, Germany, France..

In the US, professional licensure is left to the states, and most states have some form of licensing for engineers along with reciprocity for transferring a license from one state to another. Commonly, engineers have an "industrial exemption" if they work for a company that makes a product rather than offering engineering services directly to the public (such as a civil or structural engineer might do).

I've held an "engineer" title at my day job from time to time, though I'm not an engineer and have no engineering degree. Only a couple of engineers at my work site have licenses. On the other hand, my brother in law was a nuclear engineer, and all of the engineers at the power plant were licensed.

One thing you'll notice is that small companies that do contract or consulting work will call themselves "research" or "technology" rather than using the E word on their web page.