That is, it is a whole system. And largely comes to costs and known building techniques. After all, certified engineers built "galloping gerdy."
(And I didn't even get into maintenance costs and application. )
This doesn't devalue the effort of the work crew, but it does recognize you need accredited professionals at certain parts of the process to ensure public safety.
To be a bit more pointed: causality isn't difficult here. This legislation and professional practice was deliberately designed as a result of the numerous failures observed throughout the 1900s. The cause: multiple fatalities and unreliable infrastructure let to the regulation of the engineering profession. The effect: we are safer.
Whenever this question of engineering comes up it's always bridges, airplanes, and so on, but that's such a tiny percentage of engineering. Things don't have to be high-stakes to be engineering.
Those are the important parts, being real or not is irrelevant. Snake-oil selling is also a very real profession.
If all the licensing to architects, doctors, engineers, lawyers, and so on, really had a big impact on quality, the world we live in would be very different and better. But that doesn't happen because licensing a profession only works if quality is upheld on all steps of the professional education chain.
A lot of software companies circumvent all of these downsides of bad quality in education by raising the bar on the hiring pipeline with a bunch of tests and so on. Does it always work? No, just like licensing doesn't. But at least it keep la the profession accessible to those who are willing to study algorithms, data structures and so on.
There's no perfect system in our world, but I am glad we don't have license requirements to develop software. I am a statistician that became a dev through self studying, training and learning on the job, and I also know many others (even real engineers) that turned to this profession without graduating in the field and contribute a ton with their specific background knowledge.
Should everyone be called engineers? Probably not as it will elude to licensing the profession, but not calling yourself one decreases chances of finding another job dramatically.
A true tragedy tbh, I'd rather if everyone called themselves devs, scientists or something less loaded than engineer.
Depends on the country and the educational system. In some countries no such sham degree is possible to be accepted for an engineering title.
Sometimes licensing is so strict that things get done anyways ignoring license requirements because there is way more demand for some services than the supply of licensed professionals. In such cases, there are so many people violating regulation that policing becomes ineffective. It's the case with some Latin American countries.
And then you get to the problem that the license is ineffective and doesn't add to anything.
There's no perfect system to uphold quality of labor across a profession, we pick our poison and deal with it.
Setting a minimum threshold for competence makes sense, but when it becomes encoded into a legal system the result frequently becomes a way to enrich incumbents.