Fuel Line Question

Just wondering ,,,,,, why doesn't anyone use regular automotive fuel line instead of the clear / colored plastic fuel line ? Switching from flathead to clone and just wondered.
I like it because it can tell me if gas flow is a problem if its not running correctly. You can see bubbles or "non movement'.
I am going to start using it between the tank and the filter. Then I'll use the colored transparent line from the filter to the pump and from the pump to the carb. I also use transparent line for the pulse line.
Just curious....what is your preferance towards the 'more ridged' fuel line? I (myself) refer too 'see' whats going on and the flex/colored tubing looks much nicer. jmo
i have used the colored line also, but after a while it lost its flexability and got real hard. now i use the black fuel line without any problems.
as others have said you can't see flow and it's heavier and doesn't look as cool. if you want something that is transparent and doesn't get hard you can use tygon line that's the yellowish line some use.