While I agree in not everyone in a World should have the sam backround skills, I'd instead forbid some due to homeworld. It's unlikely a 18 years old boy from a TL3 world can have learned electronics or computer, or someone from a very low pop to have learned streetwise of carousing.
I'd suggest no hard rule here, but only some logic to be used but, aside from those restrictions, I agree the background learning may be varied enough as not to assume most people in a world will have the same skills.