Well a couple of reasons, but none of them from a photography point of view. There are better ones from your collection in this regard. But here's my thought:
1. Maybe I'm a person who craves calm ambience and this picture gives me exactly that.
2. It's the fact that they're enjoying their time together as a family that really got my attention, as I've been out of my home town (where my parents and one of my sisters are) for one too many years... : )