That’s because you are using your thumb! It’s the equivalent of the middle finger here. If you had an over-sized, plastic thumb you could fit over real thumb and used that for hitchhiking you’d probably get yourself killed using it!
LOL!
Just use your index finger and point to the ground at a 45 degree angle.
http://bogieworks.blogs.com/treppenwitz/2004/04/hitchhikers_gui.html
Oh, no. I’d never use my thumb, just my middle finger. That’s known over here, although the thumb is the flip-off of choice. For everyone else I use my index finger.