Specializing sounds to me like a serious effort to become very good in a certain sport. That might be an American trait, striving to become the best in something. Over here in the Netherlands that's not, with the occasional exception, the case. Most of the times it's the kid that decides which sports (plural!) it will practice in an organized setting. My nieces play soccer and ride horses. My little brother used to play soccer and practice Kempo martial arts. Me and my brothers before that played soccer and practiced Taekwon do and Kempo. The son of my late friend played soccer and practiced kick boxing. Other kids I know ride horse and play field hockey. Not out of a choice to specialize, but merely as the sports they liked most and thus wanted to spend most time on.