[api]

Qt doesn't require that but even if it did writing it 6 times is vastly more expensive. People would just rather spend 500k on writing it 6 times than 5k on a license because they are somehow offended at the notion of paying for dev software or tooling.

It's a major reason UI coding sucks. There is no incentive for anyone to make it not suck, and the work required to build a modern UI library and tooling is far beyond what hobbyist or spare time coders could ever attempt.