I'm pretty big on cuddling, and sleeping in is like heaven to me... so when someone leaves the bed before me, I'm usually the one to literally pull them back in.... LMAO. However, i usually get up at about 6am, so those days are rare. It's usually my lover that ends up complaining that i am getting up too early! hahaha
As for me: even if I really care about someone and enjoy their presence in the bed, if they get up before me, I sprawl out and I'm happy to sleep in. It's not that I'm uncomfortable when they're in bed, but I suddenly have more space, a warm spot where they were sleeping, and I like the freedom of being able to roll around without feeling like I'm gonna disturb their sleep. I'm big on not moving if I don't want to wake someone up, so being in bed alone has its advantages for me.