Does it cause poor eyesight?

Lots of use of the laptop and computer.

As a child, anyone who only stares at a distance of 30 cm becomes myopic.

Not in principle. However, it is advisable to allow the eye to recover regularly. So just look elsewhere in between.

In our family everyone is / was short-sighted, including my parents and grandparents, who grew up on farms and later learned to type on mechanical typewriters, so your statement is only partially true.