Not so much an AIBU as obviously it is up to them but I must admit I'm slightly miffed by this. I know a few couples like this, one for example that go to the GP together (and he will go in with her) for non emergency appointments, she will go to put petrol in the car and he will pop along for the ride etc.
A couple (parents) in my ds' class appear to be joined at the hip. They do pick ups together, there was a class meeting recently where due to space it was requested that only 1 parent attend and of course they both came. DS had a playdate at their house and both came to the door to meet me. I reciprocated recently and both came to my door to collect their ds.
A friend got married abroad, did a 'girls' day at her house to show the video and one woman brought her partner because it would be 'more fun'.
Again, this is light hearted and I don't think there are any social anxiety/ASD/DV issues going on, the women concerned just seem to want to be with their partners all the time.