I swear she loves taking pics of him! And doesn’t even always tell him when she does! Could mean a number of things. Maybe she takes pics too often so she’s afraid he’s going to get annoyed with it if she always tell him when she does. Or she doesn’t want him to notice so she doesn’t have to explain herself + can keep it as her secret. Or she simply wants to catch him in his natural state, just him being himself, because this is how she likes her David. It’s precious of her no matter the reason.