Everyone wants to pat dogs in videogames nowadays. You can show your affection to dogs in Enter the Gungeon, and there's a mod for making friends with dogs in Wolfenstein 3D. The world has gone dog crazy. You know patting dogs is "a big thing" because even flagrant meme bandwagon jumper Fortnite lets you do it.
Meanwhile, cats seem to have gone a bit out of fashion. Remember when everyone cared more about cats? The world seemed less complex, back then. But since we are firmly in the era of loving dogs more than cats (and who can complain about animals getting love), it's no surprise that you can now pat the dogs – any friendly dogs, not just Dogmeat – with this Fallout 4 mod. 'Pet Any Dog' is a mod created by Sagittarius22, and it pretty much does what you'd expect.
It's not completely straightforward though: you need at least Rank 1 of the Animal Friend perk. And it'll only work on friendly or neutral dogs, so don't try to pat angry and aggressive dogs: they will murder you. Meanwhile, both the player and dog must not be in combat, and you can't pat the dog while wearing power armor (that wouldn't feel nice for the dog).