> To be honest, I’m not sure why I do this.

We're in the same boat. And for a few month I've found it pretty annoying and I've tried to stop, but I haven't manage to do so. What's wrong with our brains?!

The error with your brain is that it thinks that a behavior which has been genetically engineered over millenia to be the most effective way to interact with your children should be consistent with/follow the same rules as you use in adult conversation.

Other than that, you're fine.

I think parents do this as a (subconscious?) way to help frame things from the child's perspective, knowing that the kid is terrible at taking on anyone else's perspective.

I refer to myself as 'Daddy' when talking to my cats. I don't there's any hope for me.

Since I've tried consciously not to do that, now the kid thinks "myself" is my name. I.e. says "myself" did this when the kid means "Dad did this"