Some vehicles have switched from dual exhausts back to single. It's generally about appearance over function. Some vehicles have gone back and forth over time.
The first gen Acura MDX, for example, had both styles. 2001-2003 had a single muffler exhaust system (on the left in this picture). 2004-2006 models had a dual muffler system (on the right in this picture).
^^^ That's not my photo, and I can't explain the white skull mask in the garage window!
The 2007-2013 MDX kept the dual muffler system.
The 2014 MDX has gone back to a single muffler system with a hidden tailpipe.
It's really all about the image the automaker wants to portray. Through the 2000s, there was a focus on horsepower and aggressive appearance. Lately, there's been renewed attention on efficiency. I told my dad, when they first visited us with their then-new 2014 MDX, that I presume they got rid of the dual exhaust because they were going for a "greener" appearance, he said that's exactly what the salesperson said. It's probably that way in their training materials from Acura. They're trying to draw less attention to the "power" of the vehicle.
Dodge/Ram has long been about an aggressive perception with their trucks. "Yes, it has a Hemi!" They're the first, and so far only, one to have frenched-in dual outlet exhaust from the factory. To be fair, pretty much every fullsize truck south of the Mason-Dixon line has an aftermarket exhaust with a Flowmaster setup just the way the Dodge boys have done it from the factory. I think that's a little less in vogue today than it used to be (aftermarket duals), but Dodge was following a real trend with many of its buyers by offering what they wanted from the factory.
