Oil catch cans are they needed?

Is the purpose of those cans to keep us from having to clean oil residue out of the intake? If this is a critical problem, wouldn't there be a simple black plastic can installed from the factory and the owner's manual would say empty it at every oil change?

I am seeking knowledge here, not commenting on those who have installed them.

Many old cars had only the dipstick tube and oil fill tube to vent pressure. Some incorporated vents in the valve covers.

What if the JLT can simply had a filter element instead of attaching to the intake? That way, the crankcase is passively vented and zero oil vapor is introduced into the intake.

If I remember correctly, Positive Crankcase Ventilation was born out of lowering emissions, rather than to boost performance.

I am in Florida, and we don't have annual car inspections so maintaining emissions compliance is more of a moral question than a legal one.