Why does my boyfriend watch me sleep?

Yesterday when I woke up. I opened my eyes blinked a dew times and I looked up at him. His eyes were on mine and he was smiling. I looked away and snuggled into his chest. He then said I like watching you sleep. I asked why. He said because you look at ease with yourself. It was cute. But what are other reasons? Like what was he thinking do you think while he was doing it? Lll