Weird. I'm a 6 foot tall male, and I also get asked for directions a lot. The most recent absurdity was in Paris Now, I have spent a total of maybe two weeks in Paris in twenty years, I can get by in french, but it must sound like nails on a chalkboard to a native speaker, and I'm pretty obviously american once I open my mouth. Even so, the lady who asked my advice stayed right there while I looked up the address on my phone and attempted (with limited success) to work it out.

I wonder if it really is the height.

http://professormarkvanvugt.com/images/files/heighlteadeship... is a good summary of this well-accepted effect. There are strong correlations between height and income, military rank, likelihood to be a manager, etc.

Could just be a learned behavior; Humans are born short and all the adults are tall.