The US-market sealed-style headlights are widely dismissed as mediocre, and swapping to European glass Bosch/ZKW units is seen as one of the most worthwhile upgrades and a value-adder. Complete Euro light-and-wiper conversion kits are increasingly hard to source, so cars that already have them or include the parts are called out as a plus.
US versus Euro headlights
Mercedes-Benz S-Class (W126) · cosmetic