In my experience licensing of engineers is almost exclusive to civil engineering and some other subfields. The vast majority of mechanical, electrical and software engineers will never need to be licensed.
It's also possible for unlicensed engineers to work under the supervision of a licensed engineer (PE), often the PE will be the one to stamp drawings etc.
7. Experience should be gained under the supervision of a licensed professional engineer or, if not, an explanation should be made showing why the experience should be considered acceptable.
It's also possible for unlicensed engineers to work under the supervision of a licensed engineer (PE), often the PE will be the one to stamp drawings etc.