I'm another one of those kids that always had bikes. Probably because my dad thought it was important. He cycled a lot before years on motorbikes, and I think he sees bicycles as a good life experience and a good way of learning some of life's lessons: independence, looking after something valuable and important, learning mechanical aptitude, preparedness (knowing where you're going, puncture repairs, that sort of thing). A lot of those things aren't particularly interesting for an 8 year old, so you end up learning the hard way!
Started taking the road bike I had when I was 8 further and further off road, and the grown up bike I got when I was big enough to ride one at 14 was a mountainbike - a Tim Gould Peugueot Team. Loved being out on it and rode it everywhere, mostly on my own, then with a mate when he got a Carerra. Started riding with a couple of mates at school, realised how heavy the Peugueot was, started reading mags and getting expensive ideas.
Largely resisted the expensive ideas, next 2 bikes were 2nd hand, still got one of them, new frame last year and a bitsa road bike.
Off on the bike in a sec (to ride to work) and I will enjoy it!