This may be a reason why, but it's not a great one. The vast majority of people employed in the US with "engineer" in their job title are not Professional Engineers.
I'm talking about folks that call themselves engineers, where they clearly are not. A PE has an exam with credential requirements and an apprenticeship under another PE for a period of time + having to retake that PE exam in order to get that designation. I COMPLETELY understand the PE part of it. It's the software developers that use the title of engineer that irks me. Or HR folks baiting software developers with a title of "engineer" when they clearly are NOT qualified to be that - both by credentials or by the PE designation. Engineers are engineers, scientists are scientists (and equally less qualified in comparison to engineers). Are scientists important? Absolutely .. for me, it's more about the semantics of use and the validation of it.
I wasn't particularly talking about software engineers. I have a mechanical engineering degree, and none of the ~20ish engineers at the first place I worked had a PE licence. If you want "engineer" in a job title to mean "has a PE licence", you're going to need to change the title of perhaps 95% of people currently employed in mechanical or electrical engineering. Probably more than ninety percent of aerospace engineers too. There is maybe an argument to be made that programming shouldn't be called "software engineering", but this really isn't it.
Also for whatever it is worth, I've now worked in mechanical engineering for 5 years and software for about 1 year, and they both feel the same to me. Software is sometimes faster and sloppier, but I think that's just because the build process for a program takes minutes and the build process for the CVD machines I used to design takes months.
Well, good luck with that. Back when I was in the oil business, there were even mud engineers--or mud salesmen as the toolpushers called them.
I certainly don't favor the idea that every software engineer/consulting engineer/etc. should have to get a PE before they can call themselves by that title.
You're welcome to feel differently but don't expect a lot of support.