Front signal lights, dual filament?

[SteveP]

So I was trying to replace my amber signal lights with LED and realize that the existing bulb is a dual filament (bulb size 7444NA). But the light only comes on when the turn signal or hazard button is pushed. I don't see any other instances where it would utilize 2 filament. Does anyone know why that is?

 

[KLF]

I wondered the same thing when I swapped mine out.