Any idiot can write things on a resume and say they did things they didn't do (aka lying). You would never do such a thing, of course, but as crazy as it sounds, there are people out there who would do just that! So because there's no professional license to write code, the only way to prove to these strangers that you actually can write code is some sort of exercise where you prove it to them.

I really don't get why this is so hard to understand, either. I get that live coding in front of someone else is a crazy stressful situation - I've failed multiple interviews because I couldn't perform on demand and answer the interview question in the interview setting, when I could easily have done so after taking a proverbial shower to have a think, so I'd love to get rid of them too. But unless we all band together and start a software developers guild or something, the live coding interview is here to stay. (Though, Triplebyte, now Karat, and others did take a run at improving the process, so there's that.)

I know what I know, but you don't know what I know. It's only by communicating, in a sufficiently unfakeable way, like a 45-minute in-person interview, that one can pass or fail the unwritten "can program" shibboleth.