Try using a website in an RTL language some time. Facebook and Google both support Arabic and Hebrew for example. The entire site is flipped - a left sidebar would instead appear on the right, a logo might be at the top right instead of top left, etc. Getting it right is hard, especially with mixed RTL/LTR content (like if you have a Hebrew page with some English words on it).
Try using a website in an RTL language some time. Facebook and Google both support Arabic and Hebrew for example. The entire site is flipped - a left sidebar would instead appear on the right, a logo might be at the top right instead of top left, etc. Getting it right is hard, especially with mixed RTL/LTR content (like if you have a Hebrew page with some English words on it).