Yep, brisket is a more recent cut of meat for BBQ. Remember back in the depression era, there was a demand for cheap cuts of meat that could be cooked into delicious meals and sold at a low price while still offering a margin for a profit. Pork ribs and beef brisket fit the bill. The only way to make ribs and brisket tender is to cook them for long periods of time. Well to do people didn't want them. So, that made them cheap and very desirable to a person running a BBQ restaurant. Low cost meat cooked to perfection passed on to a customer base without a lot of money but still wanting to eat something delicious that was also affordable. Those meats fit the bill very well.
Operation BBQ Relief Founding Member - I am Obsessive Compulsive about BBQ. Google it.