Wondering How to Handle Contact with Dogs in Daily Life

Salam everyone, I wanted to share something that happened recently and get your thoughts. I was at a running event with some brothers and sisters from back home, and we're all living abroad now. So, dogs are pretty common in this country. During the event, a golden retriever got excited by our big group and came over. Some folks backed away-some are scared, and some just didn't want to touch the dog, which I totally get. I gave it a pat on the head since I'm fine with dogs. Afterward, we were exchanging numbers, and one person said they'd rather I didn't touch their phone because I'd just touched the dog. I respect that-everyone has their own understanding. There are different opinions: some say dogs are pure except their saliva, others say the whole body is impure. From what I know, if you touch a dog, you just need to wash the part that came into contact before you pray. This was a running event-we were all sweaty, and no one was about to pray without showering anyway. Plus, where we live, there aren't really public prayer spaces, so we usually pray at home. So if we're going to wash up later anyway, why avoid touching the dog's owner's stuff later? Like, if I visit a friend who has a dog, sit on their couch that the dog probably sits on, but I don't touch the dog directly-do I need to wash my clothes? I'm honestly just trying to understand the reasoning-is it more about being cautious or a cultural thing since many aren't used to dogs? Jazakum Allahu khairan for any insights.