Mine does the same thing in Auto. When it's raining or otherwise low visibility, I always switch from Auto to Parking Lights or Headlights in order to turn on the marker lights to make myself more visible to other drivers, especially those approaching from behind.
2013 Surveyor SP220
2010 Silverado LT 5.3 V8
The world is a great book, of which those who never stir from home
read only a page. - St. Augustine