Personally, I feel like there is a big difference between nobody being home to open the door for a 15 year old, and no one coming to pick up an 8 year old from a party. By 15, she should have her own key, be able to let herself in, and stay home by herself. By the time I was 15, I had already been taking mass transit in NY by myself for 4 years, letting myself into my house would have been no problem. Do teens forget their keys? Sure, but it's a small thing to remember. When I was 15, I forgot my house keys, I had a half day at school. I called my mom, she said "Too bad. Now you'll just have to wait until someone gets home".
But someone forgetting to pick up a younger child, that's just irresponsible.
But someone forgetting to pick up a younger child, that's just irresponsible.