The average American hunter is not a wealthy man, and thus a bolt or lever rifle presents a far more practical, accurate, lighter, stronger, and affordable solution for NA hunting than a double. It's a matter of superior technology, hate to say it but it's a fact.

The double offers some practical advantages that are most important for DG, but that aside the double's advantages lie in the areas of romance and aesthetic appeal. The most affluent hunters place more value on the advantages of a double so that's why they are still seen in Europe. Hunting in Europe is a rich man's sport, for the most part, and tradition is very strong there both in terms of hunting methods and in terms of equipment.

It also doesn't help that most light caliber doubles are offered in calibers that are not popular in the USA.

The automotive analogy would be "Why doesn't everyone drive a vintage Rolls Royce?"

I will say that you can almost have your cake and eat it too with the Valmet (now FinnClassic 512S) system. There you have a shotgun, a DG rifle, and a North American rifle (or combo) for about the same investment you would need to make to buy a modern bolt DG rifle, an O/U shotgun, and a deer/elk rifle battery. The FinnClassic comes in Euro ctgs such as 9.3x74R, 7x57R, 7x65R, 6.5x55, as well as popular American calibers such as 30-06 and 308. The combos come in 12/222 among others, just perfect for Turkey or Coyote hunters.

I am biased, as I must disclose that I am the importer of these fine guns.