[groby_b]

Vastly oversimplified, that'd be because fonts are individual strokes of varying width and free layout that get rendered on a array of pixels with fixed sizes and fixed layout.

Resampling comes with some aliasing/information loss. Font rendering is about picking which losses you're willing to take.

And you can't just "ask designers" because the trade-offs are different based on resolution and pixel layout. And they change as you scale the font up and down. ("Font hinting" tries to fix issues with that scaling. It's got its own downsides)

And because it's fun, there's also a perception component, where different people can just look at the same font and process it differently.

Font rendering is the art of making compromises that offend the least amount of people. A good starting point on the subject: "Text rendering hates you" - https://faultlore.com/blah/text-hates-you/

(I could swear there was also a great post by Raph Levien, but I can't find it)