Why do we design for 50 ohms?

Why do we design everything for 50 ohms, what is the significance of the number, for example why not 100 ohms.

A good question, often answered; see, for example, https://www.edaboard.com/ftopic262097.html.

David

it can be found in the RF book of Thomas Lee
in a word, a tradeoff between Power handling capbility and attenuation
also because engineer likes round number.