So, a credential? In the countries and states where the title is protected (it's not everywhere), you often have to pay dues to a professional organization to claim the title. It's not enough to have the diploma, you have to pay every year too.

It is a two step process.

Engineers are only those with an university degree from an university acknowledged to actually be teaching engineering.

Then if they want to actually make use of the title, get the credential, which yes requires an yearly contribution.

Finally, in any kind of project where human lives are at stake, the engineer signing for the project has to be validated as such.

I happen to think that our profession is no different from lawyers, doctors, mechanical engineering, civil engineering, and so on.