Windows requires you to explicitly select the default audio device (can be a PITA until you know this). Basically, you need to bring multiple units online and set one as default. The "explicit" means that even if you are lucky and the one you want to be default is already, you need to assign something else, then go back and assign the one you want. You should only have to do this one time, but I found out that a new device will get assigned by Windows when installed (installed a new monitor that had sound, so had to do this again).
 
In the case of an AI for DAW use only, both the AI and Realtek need to be shown (I disable everything else that ever shows up there). Even if the Realtek is default, set the AI to default, then set the Realtek to default. The down-side is this requires another set of speakers (or you will not hear anything else), but the upside is that Windows should only see the AI as "online/offline" and allow a DAW to use it without interference.
 
Another item of note, is I uncheck the "Exclusive Mode" options at the bottom of the Advanced tab when you select a device and then the Properties button. When those are enabled, Windows can lock you out by the first application that sends sound to Windows. Most DAWs have a similar setting, which I also leave unchecked.
 
The only time I use my AI as the Windows default is for internal loopback, but the DAW is already up and online before I make that switch, and I switch it back when finished.