When I say “engineer” in disciplines other than software, I mean somebody with a professional license. You can only get that by passing exams and having a combination of experience, education and recommendations to pass a state board. It’s much harder and riskier to fake that than to make up experience on a resume or make a blog to appear like a subject matter expert. Unless you know the candidate personally, it can take a lot of effort to uncover a carefully crafted lie. Plus, recognizing quality work in software isn’t even a solved problem, to my understanding.
Other engineering disciplines hire engineers who don’t have a PE all the time. There are more engineering disciplines where taking the PE exam is the minority than the other way around.
Of course they hire non-PEs. You can’t get a license without years (at least 4) of experience first. Most consultancies I know of would not hire anyone who couldn’t pass the FE, though.
