For short frames the front wheel might be fairly close to the pedal when the crank is horizontal. If the distance is small enough, the front wheel can hit your toe as you turn the handlebars. This contact won't happen unless you turn the handlebar pretty far, much farther than you would at speed. if the front wheel hangs up on your toe, it can 1. hurt, 2. prevent teh front wheel from turning as much as it needs to.

Based on restricted front wheel motion, you might even fall. Or, if you are very quick, you might rotate the crank back to vertical really quick, and regain balance.

Toe overlap affects and frightens some people, while others are never bothered by it. It's safer not to have it, but lengthening the frame or laying back the front end to eliminate it, are not always the path to a great-handling road bike.