The adult isn't always the one making the decision. When I was a kid, I'd often be set free in the toy store and given some limit on how much I was allowed to spend. It was usually a low limit, but there was a good variety of toys under it.
The adult set the budget, but as the kid I had control over how that budget was spent, unless it was a toy my parents found objectionable.
Exactly, they had the final say. They were merely making their decision simpler. And that's the best experience you'd get. If you have family and friends, it's likely a good chunk of your toys were bought by them too. Toy makers have to appeal both to kids and adults.
The adult set the budget, but as the kid I had control over how that budget was spent, unless it was a toy my parents found objectionable.