I remember from many years ago at school, when we were talking about moral issues in RE, a scenario was presented whereby there was a group of maybe 20 people hiding somewhere extremely well hidden but in close proximity to an enemy who would kill them without a doubt if they heard them and thus discovered them.
All of the people were adults except for one, who was a young baby. The options were to either kill the baby, so that his/her cries wouldn't give them away and the rest would escape alive or not to kill the baby and almost certainly be heard and all put to death.
The choices were either for the baby alone to die, or for them all - including the baby - to die, so logically, it was obvious what to do. But it involved killing a baby. Extremely harsh position to be put in - I have an idea that the scenario was actually based on a historical event as well and not just theoretical.
So some kids desires would be for you to take them to soft play every single day even though you as an adult hate it, and it would cost you so much you could never afford any adult treats at all.
There's also the fact that wants aren't always subservient to needs, but sometimes, they are in direct opposition. Most children would WANT to eat 5kg of sweets a day. What every child absolutely NEEDS is NOT to eat 5kg of sweets a day.