The PE exam is only needed for a handful of disciplines, like civil and HVAC engineering. Even then, you only need the PE certification if you are going to be signing legal documents. You can be a civil engineer without a PE working in a team producing designs and plans that are signed by a single certified PE.
By your logic almost no one that graduated from an engineering discipline would ever be able to call themselves engineer.
You can’t compare against paralegals/lawyers because calling yourself a “lawyer” has legal implications, as in, you must be certified by the bar or you can get in trouble. It doesn’t matter which legal discipline you practice, you must be certified by the bar.
For engineers no such thing as a bar association exists for ALL disciplines. The PE certification only covers a handful of engineering disciplines therefore it can’t be a gatekeeper for all engineers. Moreover, note that certified engineers are called Professional Engineers, not just Engineers! Even the name distinguishes between certified/non-certified, it doesn’t try to take over every meaning of Engineer.