Why do we put certain word in a certain order?

I was being grumpy about the dog wanting in and out, in and out, in and out, in and out….and it struck me. He is more properly going out and in, out and in, but we never say it that way. I wonder if it’s because the word “In,” lends itself to transition to “and” more easily that “out” does. And in fact, I don’t even pronounce the and “and.” I just give an cursory “nn” sound. It’s like an extension of the “n” in “in.”

Salt n pepper is another example. I have never heard any one say “pepper and salt.”

What are some other words that you can think of that we put in certain orders, and why?