Ask HN: Why does text jump around during images load? Is it a bug or a feature?

This is a characteristic of many web pages that I can't understand. Why were solutions like this implemented, and why aren't there initiatives to solve image/video placement in a better way? I have clicked countless times on the wrong link just because an image loaded within my reaction time. Personally almost all of my work in programming has been firmware, so I'm not very familiar with the circumstances behind web page design.