I agree that kids sitting on parents' shoulders is annoying. However, it doesn't usually bother me too much unless the people in question are standing right in front of me (or if they have pushed their way in front of me).
I also agree that it isn't safe. To those parents who do put their children on their shoulders: How would you feel if your child suddenly lost their grip/balance, or they accidentally fell for any reason at all? Even if you aren't particularly tall, the injury to a small child could be very severe. Is it really worth that just so they can see the fireworks a little better?
My parents never put me or my younger siblings on their shoulders, and we have been visiting WDW since I was very young. In fact, my little brother once asked my dad to put him on his shoulders since several other kids were on their parents' shoulders, but my dad said no and explained that if he did that, other people wouldn't be able to see. Then, we got creative and everyone shifted around a bit so that my little brother could see. I guess my parents always taught me to always be courteous and polite to other people. Some parents these days don't even know the meaning of those words.
I think it is perfectly fine to try to be sure that your child enjoys his/her WDW Vacation to the fullest. However, it isn't okay to do so at the expense of other guests or at the child's safety. I've also seen parents allow their children to sit or stand on railings in order to get better views of shows and parades. Usually and luckily, a CM will come by to tell the children not to stand or sit on the railings. However, it is sad that the parents let the children do it in the first place.
Also, someone mentioned above that WDW is really all for kids. This couldn't be further from the truth. WDW is for everyone. When Walt imagined both WDW and Disneyland, he imagined parks where both parents and children could enjoy themselves together. Therefore, it isn't all about the kids, it's about everyone who comes to the parks.
