AVA author here. Not ignored, just not implemented yet. AVA is still in its infancy and we're prioritizing getting the core settled first. We're are thinking of doing something even more ambitious, though. Naive watching is easy, but we want to tackle incremental testing, so you only have to run the tests that was affected by code changes since the last run. See https://github.com/sindresorhus/ava/issues/115 for more.

We're happy to receive issues if there's anything else that bothers you. We also have a Gitter chat if you'd like to discuss: https://gitter.im/sindresorhus/ava :)