Do employees who are parents get special treatment?

Over the years, I’d hear coworkers say to the boss, “I have to leave. I need to go pick up my kids.” The boss would reply, “Sure, no problem. See you tomorrow.” Do people with kids get special treatment? If I told my boss, “I have to leave. I need to walk my dog,” something tells me that excuse wouldn’t go over very well. Does anyone ever feel like people with kids get special treatment? Did you ever say anything about it to your manager?