What Is So Unusual About This Sign?

OK so the last week or two I've seen this picture posted all over the Interwebnets, grouped with pictures such that there is an implication that it is odd, or unusual, or hilarious, or something.


Via

These signs are everywhere! ATM drive-thrus, fast food restaurants, airports, and yes bridges. Maybe they're just everywhere in Texas or something, but I just don't understand why everyone thinks this is such a unusual sign. On the contrary, it's very clever, and has been around a long time!

Speaking of drive-thrus...