Why do memes and image macros use the Impact font?
A great little video about the Impact font and its high usage in the image macro-making community. You've seen it. It's often in white letters with a thick black outline, all CAPS, and often overlaid over a funny or unusual image.
The image here shows the first ad for Impact, a typeface designed by a man named Geoffrey Lee. Through a series of sales and licensing deals, the Impact font went on to basically live on every home PC thanks to Microsoft who added the font to a small list of "standardized" web fonts.
While not necessarily "beautiful", it is functional and does a good job of making memes pop on screen. Well, now you know!