While I agree with your general point, it's nature as well as nurture. My first child who was (and is) a natural-born monkey whose idea of a good time at 18 mo

While I agree with your general point, it's nature as well as nurture. My first child who was (and is) a natural-born monkey whose idea of a good time at 18 months was leaping off a high platform to shimmy down a fireman's pole. Then we had our second child, who if anything had more freedom, more exposure to age-inappropriate toys/environments, and less supervision than our first (can't watch two kids as closely as one!)... and he'll fall off anything he tries to climb. And no, it's not a medical issue or anything, they're just not wired the same way.