Why do people from California say “the” before numbered roads and not before named roads?

I live in NY and we would say take 84 or 684. But in California they say take “the” 101 or “the”405. Also in NY we would say take “the” TSP or “the” GWB while in California they’d say take PCH. They add the “the” before numbered roads while we negate the “the”. And they negate the “the” before lettered roads where we add it. lol. Omg that was confusing AF 😂😂😂😂
Why do people from California say “the” before numbered roads and not before named roads?
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