A change of language?

I noticed tonight that Tim was using one letter words to answer a question I asked him. He had his headphones on.

Me - "Three minutes 'till bedtime! 'K?"

Tim takes his headphones off. "What?"

Me - "Three minutes 'till bedtime. 'K?"

Tim -"'K."

Tim puts his headphones back on.

Me - "Tim!"

Tim takes his headphones off and says "What dad?" Headphones back on.

Me "Can I get an okay dad?!"

Tim takes his headphones off. "What?"

Me "Can I get an okay dad?"

Tim "Okay dad."

Me "Thank you!"

Only until I went to write this, did I notice that I was using one letter words that didn't exist (that I know of) when I was young, but do exist now. I find myself in a conundrum. Is it a problem when language changes into something that U can understand but isn't what it used to be? Should I be correcting my kid on language that is being embraced by the mainstream?

I can say and you can say that it's obvious that I can't criticize the kid, while at the same time I'm using the same changes in language. My question to U is, do you accept these changes? Why and why not?