As said, they are just shortcuts to recently used and suggested apps based on different criteria such as time of day or plugged in / detected accessory. It will learn as you use the apps, and try to show you more tailored suggestions.
There's no reason to want to remove them, just use them as quick way to get to those apps. Hulu will also be there if it was recently used or the iPad thinks you may want to use it at that point in time or because you plugged in headphones and that's what you've done in the past immediately before using Hulu.
There really no reason to want to delete them. Use them as shortcuts and let them make access to those apps easier.
If you do really want to turn the feature off completely, you can go to Settings->General->Multi Tasking & Dock->Show Suggested and Recent Apps, and turn it off. This will remove the 3 right most apps from the dock which are automatically generated and never generate them again as long as its switched off.