Why is it surmised that a parallel Universe would have different laws than our own?

It is not.
They would theoretically contain every possible situation, including ones where the only difference is that your name is different.

I figure that because more discoveries are made that keep surprising physicists and astronomers about the nature of this Universe, they have begun to allow for that distinct possibility. Who knows, maybe every event that did not happen in this Universe actually played out fully in other Universes.

Maybe in a parallel Universe, dogs have the tails sticking out their noses😂🤔

It's not. Only that that's a possibility.

I think the laws of physics are the same everywhere

Some would some wouldn't

I dunno!

I'm not sure. Perhaps there would be no reason to imagine a parallel that was exactly the same as our own.🤔