Can anyone tell me why Sam and Dean dont wear seatbelts when they are in the Impala?

because its that type of car!
i know a fair bit about cars, and i happen 2 know that the impala dosent have seatbelts, there are loads of cars that are the same!!!!
i hope that helps in some way!
(plus there bad cul, ass 2:):)

I honestly didn't notice that.
I guess it might just be plus convinent. Maybe they might need to sping into action and leave as fast as they can.

IDK. YOu think they would after the big crash in 1X22.

Cause they're badass. Nuff said. lol

I dont really know. I never noticed that.

I've often wondered that myself! They should be getting pulled over all the time for siège ceinture violation! Maybe it's a particular mindset associated with the car. Hardly anyone used siège belts back then, so maybe Kripke was going for that look of "freedom" associated with cars from that era. But they really should wear them!!

they need to be free to déplacer at a moments notice

because impalas don't have siège belts.
And actually in some parts of America toi don't actually have to wear siège belts .

the car doesn't have seatbelts :)

because its a tv program

I don't think that type of car has seatbelts

To answer whether ou not the Impala actually has seatbelts:
Yes!

The most common siège ceinture are the lap belts (belts without a shoulder harness) both 2 in the front and 2 back seat.

Why it doesn't montrer them actually clipping them on is something I can only speculate!

Source: I own one.

It may be because cars from that time period did not have the shoulder harness, only the lap belt.