I don't really care either way, because you can see it in so many ways.
And people do that its best to just not care.
you can say that the person walking alone is independent and doesn't need someone else tagging along, so that makes them less of an approval junkie and less desperate for a friend or partner to follow them around places.
you can say that the couple look happy, good for them.
you can say visa versa to both.
so i think its best to not even think about it.
I don't bother with the attraction thing based on looking at someone i don't know, because its pointless and its more likely to be dissapointing.
If a girl striked up a conversation with me no matter how she looks, i find that way more interesting because it takes guts to do that. I know that when i've done that in the past, it makes that persons day, not always, but you get what i mean.
To put it another way, I used to be friends with a girl from classes, but our relationship was more brother/sister because we annoyed each other, because we knew each other well through interactions, i wasn't focussed on that she was good looking, because the looks thing passes really quickly, i dont mean that in a rude way at all, i just mean that when you hang out with people, or you are friends with them, then its more about the personality and the communication, the banter then it is the looks. (something to remember next time you go out somewhere and you see people all dressed to impress).
Looks pass really quickly, friendship is what keeps a relationship going.
Back to the original post of this thread. I'm sure females find it cute, they probably do and they are showing you respect for not hiding your affection.