Because that's how he sleeps: horizontal

Tonight is our last night in a queen-sized bed. We're getting a king-sized bed for Christmas, and are very, very excited about it. It's become very crowded in our bed lately, and an extra several inches will really come in handy. Because, as Brian and I discussed tonight, for just Brian and I, a queen-sized bed is perfect and comfortable. It's when the dogs and Sydney are added to the sleeping arrangements that the bed gets much smaller. And before you say, "Well, kick the dogs off the bed," be aware that Oliver has never slept off the bed unless by his own choice, and that it's nearly impossible to allow one dog on a bed and not the other. While the Sydney situation in the bed is just a 6:30 a.m. thing, it is still super inconvenient when I want to be comfortable beyond that time. So, in deference to that, we will compromise with our children and get a bigger bed.
Of course, I make this sound like we're doing it for the family, but really, we're doing it entirely for us, and so we can be more comfortable. Also, it means I get to buy new bed linens.