I think the most of the friends in my list asked me, most of the times because they are Nintendo loyalists and it is pretty clear that I am one too. If I send a friend's request, this is always after I had a conversation in a thread with that person and I try to show that I appreciate that person with my request.
This is all it means for me, the people in my friends list are members that I respect and like. But there are lots that I respect and like that aren't in my friend's list because we had no direct conversation yet or because I did not think of sending a friend's request in that particular moment.