Because parents have kids and before that they didn't, so they can make a solid comparison. It's not common for someone without a kid to have repeated interrupt

Because parents have kids and before that they didn't, so they can make a solid comparison. It's not common for someone without a kid to have repeated interruptions throughout the day and night and then not have any opportunity to catch up and recover from those. But it is common among parents. This reactionary and naive antagonism toward parents is silly and wrong-headed.