Because most of you really don’t care.
Also, this highlights one of the myriad of reasons that the Romney/Ryan comment about our navy having the fewest number of ships since 1917 is technically true but very misleading.
Yes, there might be fewer hulls in commission right now, but the aggregate total of America’s naval tonnage is around 2.85 million tonnes (at least in 2007 it was). In 1917, the largest ship available to the United States was 32,000 tonnes. Each of those carriers in the center column are three times that size. Each of the amphibious assault ships on the left are 25% larger than the largest ship available in 1917. And, all of that ignores just how potent and effective the air wings that these ships carry are (and we’re not even getting in to their escorts right now, which are amazing ships in their own right).
To apply their logic to something a little less esoteric than ship types and tonnage:
In 1917 the standard rifle of the army was the bolt action Springfield which fired at a rate of 15 rounds per minute (if you were good with it). The M4’s and M16’s used today can fire 60 rounds per minute in semi-automatic mode (and more in fully automatic). If Romney and Ryan were to apply their Naval thinking to firearms, they’d be asserting that 342 Springfield are better than 287 M4’s and M16’s.