My father has a unresearched and unfounded theory, which I'm beginning to buy in to, that people are pre-programmed to speak a certain amount of words a day.
So, some people are programmed with 1,000 words and some with 50,000.
When you've hit your maximum, conversation gets exhausting.
If you don't reach your quota, you feel the need to talk crap throughout dinner or while people are trying to watch a programme.
I've spent the last month in the "Why" stage with my preschooler. I've answered at least 7 million questions a day. My quota is used before 4pm and I have nothing left for adult conversation.
I think my dad might be onto something (based on my sample size of 1).