definitely in the blood, for me anyway.
My dad has had bikes since he was old enough to afford one. He used to race them, again when he could afford to.
All of my mum's brothers also raced bikes, and that's how my mum & dad met (its how all my aunts & uncles met too).
I had my first bike when I was 10, and never been without one since, although for a lot of the time it was mainly off-roaders.
The parents even brought my first off-road bikes, and my first moped.
I decided after some time ago that the off-road crashes were getting more frequent and hurting too much (I was clearly not fit enough to be competitive any more), so brought a new road bike.
Managed to persuade the wife to have a go on the back, and now we spend a couple of weeks a year touring with other bikers. She has no interest in riding herself, but likes the social side, and she actually picks the trips we go on.
For me road riding allows me to take the wife so is less antisocial than racing, where she wouldn't go as it was 'boring' apparently
I've known people killed both on & off road, and have witnessed some pretty nasty crashes, but it still doesn't put me off. I know it is a risk, but so is getting on a plane to go on holiday, or getting on the train. Simple fact is you assess the risk and decide if it is worth taking or not.
A friend of mine had a stroke a couple of years back at 39. The determination to get back on a bike is what drove him on to get better, and now, even though he is partially disabled, he is back on a trike.
His wife decided some time before that that she would no longer go on the back of his bike as to use her words 'one of them had to be sensible', meaning it limited the likelihood of both of them getting injured together.
I think bikes become a passion for whatever reason. Maybe its the company, or the thrill of the speed, or the freedom, or the sense of pride you ge from owning/riding a particular bike.
Who knows, cos I don't. I just enjoy them any way I can
Good topic though