Many people are tying a “Granny Knot”, which sits crooked and comes loose. Learn the “one simple trick” for keeping your shoes neatly and securely tied.
Why YSK: The granny knot is the most common reason as to why show laces seem to be undone so easily. It's caused when the Starting Knot & Finishing Bow don't “balance” each other. Recognizing this can help you make your shoe knots much more secure.
Edit: (BTW, YSK the website as well. It's a really good resource for tying and lacing shoes)
I started wearing them to the airport when I was traveling a lot because it's so easy to take them off/put them on while going through security in a rush. Now I just wear them everywhere!