I've had several lightning cables fail from moisture getting from my fingers onto the exposed contacts and causing galvanic corrosion. The tube from USB-C seems to prevent that.
Ah that explains why all my cords have a really tarnished lead.
Are you sure its a tarnished lead? Lots of lightning cables have one tarnished lead (often on each side) from arcing. If I remember correctly using such a cable in a new iPhone could even damage the matching pin inside the phone, leading to the situation where it would start arcing on a non-broken cable (damaging the same leads on the new cable).