[sp332]

They didn't used to, because it slowed down rendering. Then they started blurring stuff which worked well most of the time but not e.g. for retro artists who wanted the pixely look. So eventually they added some CSS properties to control it. https://builtvisible.com/image-scaling-in-css/ https://caniuse.com/#search=image%20rendering

[globuous]

wow, I just learned so much from such a simple concept !! Thanks for the links ;)