To Football Fans, how often does a TD that's under 1.5yards occur in the NFL

I am not an avid football fan by anymeans, but I do get a glimpse from time to time. I've only seen a touchdown made within 1.5yards twice, ever. The reason I'm asking is I've seen really good odds (considering how rare I've seen this happen) for "Shortest Touchdown scored Over/Under 1.5yds. ie: tonight's philly game has a -110 on Over1.5. Am I missing something?