The ones that did, learnt it at the age of 15 or 16, by modding their bycicle or model aircraft.
i never knew bicycles had tons of hi-end electronics in them. hmm maybe i need to take another look at them...
I should have used the word moped. I can only speak for the things I did on them when I was 16.
Mounted an electronic ignition, mounted an RF-remote-controlled "resistor" (to make it run the legal 40kmh instead of 75kmh)