It’s not something we did, really, but as Grandma lived round the corner, we’d drop by any time and vice versa - it wasn’t specific to a Sunday (although occasionally she’d arrange a Sunday tea, and my uncle, his wife and son would come too, by bus as they didn’t drive, and which involved them catching two buses).
Other relatives lived too far away for visits as described in the post above - if we did go, it was pre-arranged, by letter (as no-one had an phone except one aunty), and involved a day or so away. We didn’t have a car, neither parent could drive, so journeys further afield either involved the train or a coach, therefore infrequent because of cost and the practicality of getting there.
My husbands extended family of uncles, aunts, cousins and grandparents were not so far away from him when he was growing up, and his dad had a car, so they would visit nearby family either walking if close by, or in the car if slightly further afield, or sometimes the service bus if his dad was working.
It doesn’t happen like that anymore, we all contact one another by phone or text, to arrange get togethers, rather than just turn up.