So if you want the DRL's to come on, you can activate them in the ECM using AlfaOBD. I activated mine and I have a manual transmission. So mine actually come on once the truck starts moving. Also you can choose what lights come on (high beam, low beam or turn signal). Usually only trucks with the factory LED turn signals have them activated as DRL's, as incandescent bulbs would get too hot and burn out fast, hence most quad headlight setups use the high or low beam. I have the quad lamps and made my turn signals DRL's because I have LED bulbs installed.
Also if you're wondering why they don't come activated, it's mainly fleet vehicles and Canadian trucks that come like that. But sometimes you come across one that has it anyway.
Side note with the AlfaOBD, if you switch to LED bulbs, you can change the setting in the ECM and tell it you're using LED's and you won't get bulb error messages or have to use load resistors. And you can even tell the truck to use the mirror turn signal lights as marker lights instead. Not trying to sell AlfaOBD but it has been a big help making my SLT into the truck I wanted without having to take out a second mortgage lol.