Full disclosure, in high school, I once wrote an entire paper without than. I had convinced myself it wasn’t a word. Part of that was writing the paper a little too late in the evening and part of it was general confusion. The day after I turned the paper in, my teacher stopped me on the way out of class with a laugh, turns out I wasn’t the first and I’m sure I won’t be the last to make this mistake.
So given that tidbit, it should be no surprise that nearly a decade later, I still see this same mistake in other’s writing. As you can see from theoatmeal.com’s rendition, this grammar mistake is really easy to fix.