Salary sacrificing vs investing

Can someone more financially savvy than me please explain why salary sacrificing cars is so good. Every second person I speak to is singing it's praises and trying to talk me into it.

I don't get it

My car is fine and reliable,worth (outright circa $20k). Sure, I'd love a fancier car, but It's a deprecating asset

Im by no means an investing savant, I am 19, live at home and bought an investment property. What's the difference? I get negative gearing and tax advantages at the end if the financial year, salary sacrificing a car just gives instant tax advantages each pay? As far as I see they are the same tax advantages - but hopefully my asset goes up in value, a car goes down?

What am I missing? Do I have this right? I am tempted to salary sacrifice a car, but instead I'd prefer to get another investment property as I already have some equity. Are car tax advantages worth it?