> Why this weird ritual??

It's a once a year reminder that people are happy that you exist.

Sometimes children can feel like maybe their existence makes their parents lives worse, so it is important for them to be reassured that that is not the case (even if it is).

It's also just a fun thing to do. For some kids it's one of the few times per year they're allowed to go wild with sweets, so it's something they look forward to.

> If you want something just buy it.

Kids also often do not yet manage their own finances, so they don't have the freedom to just buy the things they want.